Acknowledgments The development, printing and distribution of this teacher guide has been funded through the General Education Quality Improvement Project (GEQIP), which aims to improve the quality of education for Grades 1–12 students in government schools throughout Ethiopia. The Federal Democratic Republic of Ethiopia received funding for GEQIP through credit/nancing from the International Development Associations (IDA), the Fast Track Initiative Catalytic Fund (FTI CF) and other development partners – Finland, Italian Development Cooperation, the Netherlands and UK aid from the Department for International Development (DFID. The Ministry of Education wishes to thank the many individuals, groups and other bodies involved – directly and indirectly – in publishing the teacher guide and accompanying textbook. The publisher would like to thank the following for their kind permission to reproduce their photographs: (Key: b-bottom; c-centre; l-left; r-right; t-top) Alamy Images: 69, 72; Corbis: 85; iStockphoto: 80l, 80r All other images © Pearson Education Every effort has been made to trace the copyright holders and we apologise in advance for any unintentional omissions. We would be pleased to insert the appropriate acknowledgement in any subsequent edition of this publication. © Federal Democratic Republic of Ethiopia, Ministry of Education First edition, 2002 (E.C.) ISBN: 978-99944-2-017-9 Developed, printed and distributed for the Federal Democratic Republic of Ethiopia, Ministry of Education by: Pearson Education Limited Edinburgh Gate Harlow Essex CM20 2JE England In collaboration with Shama Books P.O. Box 15 Addis Ababa Ethiopia All rights reserved; no part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise without the prior written permission of the copyright owner or a licence permitting restricted copying in Ethiopia by the Federal Democratic Republic of Ethiopia, Federal Negarit Gazeta, Proclamation No. 410/2004 Copyright and Neighbouring Rights Protection Proclamation, 10th year, No. 55, Addis Ababa, 19 July 2004. Disclaimer Every effort has been made to trace the copyright owners of material used in this document. We apologise in advance for any unintentional omissions. We would be pleased to insert the appropriate acknowledgement in any future edition Printed in Malaysia Contents Introduction to the Teacher’s Guide 5 Unit 1 Vectors 13 1.1 Representation of vectors 1.2 Addition and subtraction of vectors 1.3 Some applications of vectors 13 16 20 Unit 2 Motion in a straight line 23 2.1 Uniform motion 2.2 Uniformly accelerated motion 23 26 2.3 Graphical description of uniformly accelerated motion 2.4 Equations of uniformly accelerated motion 2.5 Relative velocity in one dimension 28 31 34 Unit 3 Force and Newton’s laws of motion 37 3.1 3.2 3.3 3.4 3.5 3.6 3.7 37 40 43 45 47 50 51 Forces in nature Newton’s second law Frictional force Newton’s third law Conservation of linear momentum Collisions The rst condition of equilibrium Unit 4 Work, energy and power 54 4.1 4.2 4.3 4.4 55 57 60 63 Mechanical work Work–energy theorem Conservation of energy Mechanical power Unit 5 Simple machines 66 5.1 Purposes of machines 5.2 Inclined plane, wedge and screw 5.3 Levers 66 69 72 Grade 9 3 Contents Unit 6 Fluid statistics 77 6.1 Air pressure 6.2 Fluid pressure 77 81 Unit 7 Temperature and heat 86 7.1 Temperature and heat 7.2 Expansion of solids, liquids and gases 7.3 Quantity of heat, specic heat capacity and heat capacity 7.4 Change of state 86 89 Unit 8 Wave motion and sound 97 8.1 8.2 8.3 8.4 Wave propogation Mechanical waves Properties of waves Sound waves Grade 9 Minimum Learning Competencies Grade 9 Syllabus 4 92 94 97 100 103 107 112 116 Grade 9 Unit 1 Introduction to the Teacher's Guide Some general aims of physics education Physics is an important subject that contributes to the development of our country in many ways. A knowledge and understanding of physics helps students to understand the world and appreciate how it works. It contributes to a society that benets from this understanding, and produces people who realise how the environment can be exploited in a sustainable way for the benet of society. It prepares students for employment, both in a general way and as a preparation for careers that require knowledge of the subject, such as engineering or communications. However, a study of physics does not just mean learning facts. Physics, as with the other sciences, requires the student to develop problemsolving skills. e secondary physics curriculum takes a competency-based, active learning approach, underpinned by three broad outcomes: knowledge, values and attitudes, and skills. e Students’ Book and Teacher’s Guide places emphasis on learnercentred classroom and eld activities, not only to help students to acquire knowledge, but also to develop problem-solving and decision-making skills, as well as a good attitude to society and the world around us. e teacher must make the students aware that science is a dynamic activity, a body of knowledge that constantly grows and is modied by experimentation. He or she can utilise new approaches to teaching and learning, involving a range of teaching styles, along with practical activities and eld work, summarised in the ‘Teaching methods’ section below. General objectives of the Grade 9 physics course When students have completed Grade 9 physics they should be able to: t6OEFSTUBOEUIFCBTJDDPODFQUTPGQIZTJDTUIFMBXTPGEZOBNJDTBOEFYQMPSF dierent kinds of forces, the quantication and forms of energy (mechanical, sound, light, and thermal), and the way energy is transformed and transmitted, the concepts and units related to energy, work, and power and the laws of conservation of energy and of momentum for objects moving in one dimension. t%FWFMPQNBOJQVMBUJWFTLJMMTJOTPMWJOHQSPCMFNTSFMBUFEUPUIFMBXTPG conservation of momentum and energy. t6OEFSTUBOEPGUIFQSPQFSUJFTPGNFDIBOJDBMXBWFTBOETPVOEBOEUIF principles underlying the production and transmission of mechanical waves and sound; the properties of light and the principles underlying the transmission of light through a medium and from one medium to another. t%FWFMPQTDJFOUJDJORVJSZTLJMMTBTUIFZWFSJGZBDDFQUFEMBXTBOETPMWFCPUI assigned problems and those emerging from their investigations. t"OBMZTFUIFJOUFSSFMBUJPOTIJQTCFUXFFOQIZTJDTBOEUFDIOPMPHZBOEDPOTJEFS the impact of technological applications of physics on society and the environment. t4PMWFUIFQSPCMFNTVTJOHBWBSJFUZPGQSPCMFNTPMWJOHTLJMMT Grade 9 5 Introduction Each unit of study has specic learning competencies, and these are listed at the beginning of each unit in both the Students’ Book and the Teacher’s Guide, providing a useful checklist for both students and teachers. Teaching methods e subject content can be delivered in dierent ways in order to achieve the specic objectives. e type of teaching method used will aect the skills and attitudes that the students develop. e teacher will want to use the most eective methods for teaching a particular topic. In physics, it is recommended that the teacher use more than one teaching method in a single lesson – the discussion method might be suitable for the beginning of the lesson, followed by the discovery method, or a practical activity. e strengths and weaknesses of a range of dierent methods are summarised in the table below: Method Strengths and weaknesses Lecture – content is delivered Students receive correct factual information from the teacher. to students by teacher 6TFGVMUPTUJNVMBUFUIJOLJOH Students develop skills such as identication, observation, recording, making predictions, synthesis, analysis and drawing conclusions. Students develop qualities such as self-condence, curiosity and inquiry. 6TFGVMGPSMBSHFOVNCFSTPGTUVEFOUT Makes students passive because it is one-way communication. Makes learning dicult to assess. Discovery – teacher guides Students develop skills such as identication, observation, recording, students to discover scientic making predictions, synthesis, analysis and drawing conclusions. facts for themselves Students develop qualities such as self-condence, curiosity, interest and co-operation. Discussion – sharing of ideas Allows sharing of each other’s ideas. between students and teacher Can be useful at start of a lesson to motivate students. Allows everyone to participate actively. A few people may end up dominating the discussion. Not easy to conduct for large classes. Can be time-consuming. Teacher can easily lose track of the argument. Question and answer – teacher6TFGVMGPSHBVHJOHTUVEFOUTVOEFSTUBOEJOHPSLOPXMFEHFP asks questions, students answer. concept. Students also ask questions 6TFGVMGPSCFHJOOJOHBOEFOEJOHBMFTTPO Need to ensure sucient questions are framed to stimulate thinking – closed questions do not achieve this. Can be counterproductive if the teacher asks too many questions. 6 Grade 9 Introduction Problem solving – students Students develop skills such as identication, observation, recording, are presented with an exercisemaking predictions, synthesis, analysis and drawing conclusions. where they must nd an answerStudents develop desirable qualities such as seeking knowledge, to a problem curiosity, enquiry and responsibility. Worked examples in the Students’ Book can usefully be presented as problems for students to solve – see notes for each topic for further details. Can waste time if not properly planned and guided. Students have the opportunity to research a topic and look for information on their own. Assignments – specic task given to students to nd out about a particular problem or issue Worksheets – handouts to Allows students to think for themselves without outside inuence. guide students in practical workAllows individual ideas to be shared in a group. Demonstration – teacher Students develop skills such as identication, observation, recording, carries out practical work making predictions, synthesis, analysis and drawing conclusions. if materials/equipment are Students develop desirable qualities such as self-condence, curiosity, inadequate or the procedure interest and cooperation. is too complex or unsafe for students Practical activities – students Gives teacher an opportunity to develop students’ interest in the carry out practical work subject. individually or in groups; Teacher has opportunity to interact with students. students gain hands-on Teacher provides the standard/expected results for each activity. experience Can be used with discussion method (during discussion of results). is method is highly Students develop skills such as identication, observation, collecting, recommended and should be measurement, manipulation, data recording, investigation, making used as much as possible. predictions, interpretation, evaluation, synthesis and drawing conclusions. Students develop desirable qualities such as self-condence, curiosity, interest and co-operation. Field work – outdoor learning Helps students develop skills such as identication, observation, activity collecting, measurement, data manipulation, recording, analysis, report writing and verbal reporting. Students appreciate the environment. Can waste time if not properly planned and guided. Project – short- or long-term Helps students develop (among others) report-writing, presentation investigation and data analysis skills. Students develop skills in using scientic methods. Can be time-wasting if not properly planned and guided. Case study – study carried Allows students to apply new knowledge and skills. out on a particular natural Allows development of analytical and problem-solving skills. environment, then applied to Allows exploration of solutions for seemingly complex problems. another similar setting Students may not see application to their own situation. Students may get wrong results due to insucient information. Grade 9 7 Introduction Schemes of work, lesson plans and records of work A scheme of work is a plan for how the topics in the syllabus will be covered over the course of the year. e scheme should be based on the secondary physics syllabus. e construction of a scheme of work is an important role of a teacher. In this Teacher’s Guide, a sequence of activities is suggested for each topic. However, it may be necessary to vary this sequence from one school to another depending on factors such as funding, laboratory facilities, seasonal availability of teaching materials and time available for teaching, in addition to teacher preferences. An eective scheme can be developed and modied over a period of time, improving it from year to year as a result of teachers’ experience. Schemes of work should always be prepared at the beginning of the school year. It is easier to keep so copies that can be updated when necessary. A lesson plan acts as a guide for the teacher, outlining the activities that will be carried out in order to achieve the specic objectives of the lesson. Lesson plans are vital to ensure that teaching and learning are focused on objectives to be achieved but teachers should not be afraid to deviate from plans occasionally if necessary for the students. A record of work is compiled aer every lesson. It is a brief report summarising what has been covered in the lessons. e record of work should note areas of deviations from the lesson plan and reasons for this. Time spent reecting on a lesson is time well spent since it enables more eective teaching and learning. It is hoped that the schemes of work and ideas for lesson plans in this Teacher’s Guide will motivate teachers to develop their own schemes and lesson plans to suit their preferred teaching methods and resources available in their school. Each topic in this book contains the following sections: tMFBSOJOHDPNQFUFODJFT tTVHHFTUFETDIFNFPGXPSLGPSFBDIUPQJD tHVJEFMJOFTGPSQSBDUJDBMBDUJWJUJFT tTLJMMTBOEBUUJUVEFTUPCFEFWFMPQFE tBOTXFSTUPRVFTUJPOTJOUIF4UVEFOUT#PPL Assessment: tests and examinations Assessment helps you identify whether learning has occurred, and is part of the teaching and learning process. e syllabus and minimum learning competency documents (included at the back of this teacher guide) give a large number of objectives that students are expected to achieve during the year. e review questions and end-of-unit questions are set to help test these. However, it is unlikely that teachers will be able to test every single objective in a term or year: if we did that, there would be probably little or no time le for teaching! ere is in fact a danger that we spend too much time testing and too little time teaching. We want to avoid this danger; yet at the same time it is important to meet the requirements of the syllabus, which indicate that we should do our best to nd out, in one way or another, how far we have achieved the objectives set at the start of a given unit. e answer is that we should carry out continuous assessment. is means that in the course of ordinary classroom teaching, and setting and marking assignments, we need to keep a record of how well the class does. 8 Grade 9 Introduction Continuous assessment helps teachers to ensure that all students have the opportunity to succeed in school – in any class there may be a wide range of abilities or needs, and by using continuous assessment, teachers can adapt their approach to all of them. e teacher should continually observe the students to see what they know and can do. ere are many dierent kinds of assessment activities included in this course: some, like the review questions, ask students to recall information, while others, such as the boxed activities, focus on processes such as analysis, constructing or showing a skill. ere is a wide range of approaches that can be used for this, including classroom experiments, eld trips, debating, role play, and research projects. In both continuous assessment and regular testing/exam-setting, teachers should assess all aspects of knowledge and understanding - knowledge, comprehension, application, analysis, synthesis and evaluation. Knowledge means recalling previously learned information, such as terminology, classications, sequences and methods. In tests, some of the key words used for this sort of question are: list, dene, describe, label, name. Comprehension means understanding the meaning of information. A comprehension question uses key words such as: summarise, interpret, contrast, predict, distinguish, estimate, discuss. Application is the use of previously learned information to solve problems in new situations. It is identied by key words such as: demonstrate, calculate, complete, illustrate, relate, classify. Analysis means the breaking down of information into its component parts, examining and trying to understand such information to develop conclusions by identifying causes, making inferences and/or nding evidence to support generalisations. Questions contain key words such as: explain, separate, order, arrange, compare, select, compile. Synthesis means applying prior knowledge and skills creatively to produce a new or original thing. Questions contain key words such as: plan, rearrange, combine, modify, substitute, rewrite. Evaluation means judging the value of something based on personal opinion, resulting in a nal opinion, with a given purpose, without really right or wrong answers. Students might have to compare and discriminate between ideas, assess the value of some evidence of a theory, or make choices based on a reasoned argument. Examples of key words are: assess, recommend, convince, select, summarise, criticise, conclude, defend. Model lesson plan Topic: Graphical description of uniformly accelerated motion Sub-topic: Velocity–time graphs %VSBUJPONJOVUFT Class: Grade 9 %BUF'FCSVBSZ Rationale JTJTUIFTFDPOEMFTTPOJOUPQJD*OUIJTMFTTPOTUVEFOUTXJMMMFBSOIPXUP draw and interpret velocity–time graphs. Grade 9 9 Introduction Lesson objectives By the end of the lesson students should be able to: tESBXBOEJOUFSQSFUWFMPDJUZoUJNFHSBQIT Prerequisite skills and knowledge: tTUVEFOUTXJMMOFFEUPIBWFFYQFSJFODFPGEJTUBODFoUJNFHSBQIT Teaching/learning resources IUUQXXXQIZTJDTNDMBSFOIJHIDPN'MBTI.PUJPO%JBHSBNIUNM Stage (time) Introduction NJOVUFT %FWFMPQNFOU NJOVUFT Teaching and learning activities Introduce velocity–time graphs and ask students to work with a partner to FYQMBJO'JHVSF5BLF feedback of ideas. Learning points Students should be able to tell you the velocity at points where the graph changes and explain what is represented by a horizontal line in a velocity–time graph (constant velocity). ey should also realise that straight slopes on such graphs represent contsant acceleration (negative slopes represent deceleration). %JWJEFUIFDMBTTJOUPStudents TNBMM need to be able to interpret constant velocity, HSPVQT%SBXUIFHSBQIT constant acceleration but JO'JHVSFPOQBHF PGUIF4UVEFOUT#PPL distinguish where one on the board but leave acceleration is greater than another, deceleration out the descriptions. e students have to work in and changing acceleration. their groups to provide descriptions of what the graphs are showing. Allow NJOVUFTNBYJNVN for this and then take feedback. Work through the worked FYBNQMFPOQBHFPG the Students’ Book as a class. Students should be suggesting the method to you to ensure that they are actively involved in the Students were introduced solution. to interpreting travel Students should work with graphs as a ‘story’ at the a partner to tackle Activity end of the last lesson. 10 Grade 9 Introduction Summary and Introduce the animation DPODMVTJPONJOVUFT on the website given above for students to FYQMPSF%JTDVTTXIBUJUJT illustrating. Evaluation Students should begin to UBDLMFSFWJFXRVFTUJPOT BOEXJUIBQBSUOFSJT can be completed at home individually if necessary. Students have oppertunity to ask questions and comment on the activity – they may be asked to write a summary of the lesson for homework. Note taking %VSJOHQIZTJDTMFTTPOTTUVEFOUTTIPVMECFBDUJWFMZJOWPMWFEJOUIFJSMFBSOJOH*U is important that they develop strategies for recording what they are doing in the lesson which will enable them to revisit the concepts away from the classroom, either to complete assignments or to revise for tests. Practical activities should be recorded in such a way that another person could repeat the activity at a later date (this is the principle on which scientic papers are written and, although we do not need students to go into quite the detail given in such papers, we do want them to begin to learn to record practical work accurately). e following headings are recommended for a practical report: t"JNPGBDUJWJUZ t"QQBSBUVTVTFEXJUIEJBHSBN t.FUIPE t3FTVMUTXIJDINBZJODMVEFOVNFSJDBMEBUBXIJDINBZCFQSFTFOUFEBTBUBCMF and/or graph). Conclusion Students should be taught that sometimes results from practical work are not quite as the theory may predict – they should be encouraged to see this as a positive learning experience and be taught that they should never attempt to t results to the theory but rather explain why their results may not t the theory (even if the explanation turns out to be that they did not take measurements accurately enough)! When summarising the main learning points of the lesson, as indicated in the lesson plan above, students can use the methods listed here. Grade 9 11 Introduction 6TJOHCVMMFUQPJOUTUPTVNNBSJTFUIFNBJOQPJOUTGPSFYBNQMFGSPN above, these would be: t0OBWFMPDJUZoUJNFHSBQIBIPSJ[POUBMMJOFSFQSFTFOUTBDPOTUBOU a positive slope represents a constant acceleration and a negative slope represents a constant deceleration. t"TUFFQFSTMPQFSFQSFTFOUTBHSFBUFSBDDFMFSBUJPO t"DVSWFEMJOFSFQSFTFOUTBDIBOHJOHBDDFMFSBUJPO tFBSFBVOEFSBWFMPDJUZoUJNFHSBQISFQSFTFOUTEJTQMBDFNFOU Constructing a spider diagram, for example, for the lesson above, this would look like: AREA UNDER CURVE DISPLACEMENT horizontal line CONSTANT VELOCITY steeper slope greater acceleration CHANGING DECELERATION VELOCITY–TIME GRAPHS CHANGING ACCELERATION CONSTANT ACCELERATION CONSTANT DECELERATION steeper slope greater deceleration 12 Grade 9 Vectors Learning Competencies for Unit 1 By the end of this unit students should be able to: t %FGJOFUIFUFSNWFDUPS Unit 1 This unit should GJMMBQQSPYJNBUFMZ 9 periods of UFBDIJOHUJNF t (JWFTPNFFYBNQMFTPGWFDUPSRVBOUJUJFT t 3FQSFTFOUWFDUPSTCPUIBOBMZUJDBMMZBOEHSBQIJDBMMZ t %FGJOFUIFUFSNSFTVMUBOUWFDUPS t "EEUXPWFDUPSTUPHFUIFSJODMVEJOHWFDUPSTJOUIFTBNFEJSFDUJPO PQQPTJUFEJSFDUJPOTBOEBUSJHIUBOHMFTUPFBDIPUIFS t %FUFSNJOFUIFBOHMFPGBSFTVMUBOUWFDUPS t 6TF1ZUIBHPSBTTUIFPSFNUPEFUFSNJOFUIFTJ[FPGUIFSFTVMUBOUWFDUPS t 3FTPMWFBWFDUPSJOUPIPSJ[POUBMBOEWFSUJDBMDPNQPOFOUT t 'JOEUIFEJSFDUJPOBOESFTVMUBOUPGUXPPSNPSFWFDUPSTVTJOHUIF DPNQPOFOUNFUIPE t %FGJOFUIFUFSNFRVJMJCSJVN t &YQMBJOUIFJNQPSUBODFPGGPSNJOHBUSJBOHMFPGUISFFWFDUPST t $BSSZPVUTPNFFYQFSJNFOUTUPJOWFTUJHBUFWFDUPST 3FQSFTFOUBUJPOPGWFDUPST Learning competencies 5IJTTFDUJPO TIPVME GJMMBQQSPYJNBUFMZ 2 periods of UFBDIJOHUJNF #ZUIFFOEPGUIJTTFDUJPOTUVEFOUTTIPVMECFBCMFUP v %FGJOFUIFUFSNWFDUPS v (JWFTPNFFYBNQMFTPGWFDUPSRVBOUJUJFT v 3FQSFTFOUWFDUPSTCPUIBOBMZUJDBMMZBOEHSBQIJDBMMZ Starting off Vectors are very important in physics; however, at this stage their importance is rather hidden. It is not until students use complex mathematics that their importance comes to the fore. Students should be encouraged to think about the quantities they are measuring and what they actually mean. is will help them to distinguish between vectors and scalars. Representing vectors is limited to scale diagrams and simple analytical descriptions; there is no need to develop vector notation as part of this topic. Grade 9 13 6OJU7FDUPST Teaching notes is rst section is quite short. It provides students with a simple overview of what vectors are and how they might be represented. Ask the students to come up with a list of dierent properties of an object that could be measured. Perhaps provide them with some examples: an apple, a moving bus, the Moon. In pairs they could try to arrange these properties into groups of their own devising. Explain that all quantities are either scalar or vector quantities. Stress that all vector quantities must include a direction. Use the example of describing the position of a nearby town. It may be a distance of 12 km away but that does not give us enough information to be able to nd it. e displacement is 12 km East. Students will benet from plenty of examples: perhaps the easiest to understand are forces, displacements and velocities. Once you have explained vectors and scalars, students could look again at their list and classify their properties as either vectors or scalars. Common issues arise around the following: Activity 1.1: Answer Scale: 1 cm: 100 km Quantity Vector or Scalar? Issue(s) Temperature Scalar Because temperature can be negative, some students associate this with a negative direction and so assume it is a vector. is mistake can be easily remedied by discussing that a temperature of 12°C West makes no sense. e negative is relative to the freezing point of water; it is not related to direction. Kinetic energy Scalar Some students will assume this is a vector, especially as it depends on the velocity of the object. Take time to explain that all energies are scalars; they are a measure of how much work the object can do. Energy does not depend on the direction; two identical cars travelling in dierent directions have exactly the same kinetic energy. Distance Scalar Some students muddle distance with displacement. At this stage it is worth stressing to them that distance is a measure of how far you go, whereas displacement is distance in a particular direction. Again, examples may help to illustrate this. 4 cm 45° 400 km North East Scale: 1cm: 8m/s 4 cm 60° 32 m/s at an angle of 60° to the horizontal t 4UVEFOUThPXO BOTXFST Students should be encouraged to draw arrows to represent vectors. Take time to carefully explain the importance of scale and direction. Give a few examples drawn carefully on the board. Show the importance of scale, but keep it simple (e.g. 10 cm = 1 m/s or 1 cm = 20 N). 14 Grade 9 6OJU7FDUPST Students should draw a range of dierent-sized vectors acting in dierent directions. Make up a list and ask them to draw an arrow for each. Try to include examples of force, velocity, acceleration and displacement. Additionally ensure that they will have to use dierent scales. For example, get them to draw 10 N up. is might involve a scale of 1 cm = 1 N. en get them to draw 5000 N le. is clearly needs a dierent scale! Perhaps 1 cm = 500 N. e importance of taking time and care when drawing these diagrams should be stressed. is topic may also be used to review the correct use of metric units, in particular cm, m and km. To extend this and get students to measure vectors, you could issue them a sheet with dierent vectors drawn at dierent scales, and ask them to determine the size and direction (so angles will need to be measured) for each vector. Alternatively, they could make up their own and test a partner. SA = starter activity MA = main activity CA = concluding activity Definition and examples of vectors SA -JTUEJGGFSFOUQSPQFSUJFTPGBOPCKFDUUIBUDPVMECFNFBTVSFE MA (JWFFYBNQMFTPGWFDUPSTBOETDBMBST%JTDVTTJPOBDUJWJUZPOQBHFPG4UVEF CA 3FWJFXRVFTUJPOT¦ Representing vectors analytically and graphically SA 4UVEFOUTXPSLJOQBJSTUPTPSUQIZTJDBMRVBOUJUJFTJOUPWFDUPSTBOETDBMBST MA 4UVEFOUTESBXWFDUPSTUPTDBMF CA 3FWJFXRVFTUJPOT¦ Activities t$PNQJMFMJTUTPGRVBOUJUJFTBOEDMBTTJGZUIFNBTTDBMBSTPSWFDUPST t1SBDUJTFESBXJOHBSSPXTUPSFQSFTFOUWFDUPST*ODMVEFUIFVTFPGEJFSFOUTDBMFT and angles. t%FUFSNJOFUIFTJ[FBOEEJSFDUJPOPGWFDUPSTGSPNEJBHSBNT Resources http://www.zonelandeducation.com (Physics Department, Mechanics, Vectors, Introduction) Where next? Once the basic ideas of vectors are understood, students move on to adding up vectors using graphical and simple mathematical methods. is topic is developed further in Grade 11. Grade 9 15 6OJU7FDUPST Answers to review questions 1. Any four from: force, displacement, electric current, momentum, moment, velocity, acceleration, displacement. 2. Vectors include a size and a direction; scalars are size only. Suitable examples. 3. ree vectors drawn to scale; check using a ruler. 4. 10 N magnitude in an upwards direction. 5IJTTFDUJPO TIPVME "EEJUJPOBOETVCUSBDUJPOPGWFDUPST GJMMBQQSPYJNBUFMZ 5 periods of Learning competencies UFBDIJOHUJNF #ZUIFFOEPGUIJTTFDUJPOTUVEFOUTTIPVMECFBCMFUP v %FGJOFUIFUFSNSFTVMUBOUWFDUPS v "EEUXPWFDUPSTUPHFUIFSJODMVEJOHWFDUPSTJOUIFTBNFEJSFDUJP PQQPTJUFEJSFDUJPOTBOEBUSJHIUBOHMFTUPFBDIPUIFS v %FUFSNJOFUIFBOHMFPGBSFTVMUBOUWFDUPS v 6TF1ZUIBHPSBThTUIFPSFNUPEFUFSNJOFUIFTJ[FPGUIFSFTVMUBOUWF v 3FTPMWFBWFDUPSJOUPIPSJ[POUBMBOEWFSUJDBMDPNQPOFOUT v 'JOEUIFEJSFDUJPOBOESFTVMUBOUPGUXPPSNPSFWFDUPSTVTJOHUIF DPNQPOFOUNFUIPE Starting off is section is essentially revision of Pythagoras’s theorem and trigonometry applied to vectors. It serves to highlight the key dierence between vectors and scalars. ere is plenty of opportunity for students to practise drawing and solving vector problems. is could be done individually or working in small groups. Teaching notes In this section students will be challenged to add dierent vectors, including vectors that are perpendicular to each other. To start this section you could write on the board 6 + 6 = ? and ask the students for answers. Hopefully most will say 12! Go on to explain that because all vector quantities include a direction it is possible for the answer to be 12, but also it might be 0, or even 8.5 (if the two vectors are at right angles). Ask students to think about how that might be possible. Some may even suggest the idea of dierent directions and angles. Demonstrate how scalars are added together using simple arithmetic. Give a couple of examples (including negative values of temperature). Explain how, when vectors are added together, the overall vector is called the resultant. Go back to the 6 + 6 = ? and explain how it is possible to get a resultant vector of 12 and a resultant vector of 0. 16 Grade 9 6OJU7FDUPST Limiting it to parallel vectors, give examples using diagrams on the board. For example: Activity 1.2: Answers 6N + 3 N = 9N vLNMFGU vLN4PVUI vLN8FTU 6N + 3 N = 3N Activity 1.3: Answers Relate vectors to real-life situations: for example, walking up and down a bus orv train moving in a particular direction. 1 cm: 5 km m 5k 22. Explain that the direction of the vector is really important and that it is oen the convention for one direction to be classed as positive and the other negative, but which way around is arbitrary. 20 km Using the example in the diagram above, the second version could be written as: 62° 6 N + –3 N = 3 N 10 km is would mean the positive direction is dened as le to right. 6 N is positive, as 22.5 km at 62° to it is to the right; as the 3 N is to the le, it is negative (–3 N). the horizontal 1 cm: 50 km m .1 k 158 Ask the students to determine the resultant vectors from a number of dierent v problems. Give them plenty of examples, and again use dierent kinds of vectors for each one (displacement, force, velocity, acceleration, etc). Ensure that in a couple of examples the resultant vector is 0. It should be stressed that dierent vectors could add up to no overall vector: eectively they all cancel each other out. 150 km is could be extended by providing three or four vectors, although these should 70° be limited to parallel vectors at this stage. 50 km .6 15 Take time to explain the parallelogram method, giving a worked example on the board. Limit this to perpendicular vectors. Get the students to practise this technique, providing them with several examples of perpendicular vectors. Remind students of the importance of measuring the angle and the selection of the scale in each case. Try to relate the examples to real situations. 14 km km Ask students how they would nd the resultant vector if the two vectors to be 160 km at 70° to the horizontal added were not parallel, but instead perpendicular. Give the example of travelling v to a town that is 10 km North and 5 km West of their current position. How could 1 cm: 2 km they nd their resultant displacement? Ask students to look carefully at their diagrams, and ask them if they could determine the size of the resultant mathematically. Explain that Pythagoras’s theorem could be used to determine the size of the resultant vector. 63° Pythagoras’s theorem “e square of the hypotenuse of a right-angled triangle is equal to the sum of squares on the other two sides.” 7 km 15.6 km at 63° to the horizontal the a2 = b2 + c2 a b c Grade 9 17 6OJU7FDUPST Activity 1.4: Answer v 125 N Give students a few examples and take time to explain that the resultant is the hypotenuse. Ask them to mark on their diagrams the right-angled triangle and use a red line to conrm the resultant is the hypotenuse. Stress that all vectors must include a direction and that this may be calculated using trigonometry. B 85 N Trigonometry A opposite 40° 20° Resolve B: BH = 125 x cos 60° = 62.5 N BV = 125 x sin 60° = 108.25 N Resolve A: AH = 85 x cos 20° = 79.9 N AV = 85 x sin 60° = 29.1 N Total horizontal: = 62.5 + 79.9 = 142.4 N Total vertical: = 108.25 + 29.1 = 137.35 N 137.35 N R 142.4 N tan = 137.35 142.4 = 44° R2 = 142.4 2 + 137.35 2 R= 39142.78 R= 198 N Resultant is 198 N at 44° to the horizontal adjacent hypotenuse Students nd this quite dicult to remember. Perhaps use SOH-CAH-TOA to help. SOH: sin = opposite / hypotenuse CAH: cos = adjacent / hypotenuse TOA: tan = opposite / adjacent Provide the students with 10 dierent triangles with values for the opposite and adjacent sides. Get them to calculate the hypotenuse and angle in each case. ey could use the examples they have drawn using the parallelogram rule. is could be extended using several dierent vectors, some parallel and some perpendicular. First the students add up the parallel vectors to give a resultant horizontal and a resultant vertical vector. ese may then be added using the mathematical method described above. Think about this… What are the advantages of the parallelogram method over using mathematics to solve vector problems? Discuss this with the students, and include the concept of the simplicity of the parallelogram method over the precision of the mathematical method. Provide the students with a simple recap and then ask: what if the vectors are not parallel and not perpendicular? For example: 6.0 N 60° Show them how this could be solved using the parallelogram method and highlight the fact that, as the vectors are not perpendicular, the parallelogram is not a rectangle. If necessary, students could draw a few examples. 18 Grade 9 6OJU7FDUPST Explain that to solve this mathematically, the vector at the angle must be ‘resolved’. is means splitting it into two components, one horizontal and the other vertical. is would give one vertical and two horizontal vectors, which could then be added as above. rough diagrams, show how one vector may be resolved into the two components. is is further practice of trigonometry. Give the student a few examples of vectors to be resolved. When they are happy resolving vectors, show them how to add up the components to determine the resultant vector. Extend by providing examples where two or more vectors must be resolved to determine the resultant. SA = starter activity MA = main activity CA = concluding activity Combining vectors SA %JTDVTTIPXUPDPNCJOFGJSTUTDBMBSTBOEUIFOWFDUPST MA "DUJWJUZ CA 3FWJFXRVFTUJPOBOEEJTDVTTJPOBDUJWJUZ Pythagoras’s theorem and vectors SA "TLTUVEFOUTUPFYQMBJOIPXab and cJO'JHVSFBSFSFMBUFE MA %JTDVTTFYBNQMFTPGVTFPG1ZUIBHPSBTTUIFPSFNJODMVEJOHWFMPDJUJFTGPSDF CA %JTDVTTJPOBDUJWJUZPOQBHFPG4UVEFOUTh#PPLBOESFWJFXRVFTUJPO Non-parallel and non-perpendicular vectors SA %SBXWFDUPSTBOEBTLGPSJEFBTPOIPXUPDPNCJOF MA "DUJWJUZ CA 3FWJFXRVFTUJPOBOEBTLTUVEFOUTUPFYQMBJOQBSBMMFMPHSBNNFUIPEJOUIFJSP Resolving vectors (1) SA "TLTUVEFOUTUPFYQMBJOIPXUPTPMWFBSJHIUBOHMFUSJBOHMFVTJOH1ZUIBHPSBTT MA 4UVEFOUTXPSLJOHSPVQTUPSFTPMWFWFDUPST CA 4UVEFOUTNBLFVQFYBNQMFTPGWFDUPSTUIBUOFFESFTPMWJOHGPSUIFJSQBSUOFS Resolving vectors (2) SA "TLTUVEFOUTUPUFMMZPVIPXUPSFTPMWFFBDIWFDUPSJO'JHVSFJOUIF4UVEFOUTh#P MA "DUJWJUZ CA 4UVEFOUTNBLFUIFJSPXOTQJEFSHSBNGPSUIJTUPQJDCBTFEPOUIFTVNNBSZPOQBHF 4UVEFOUTh#PPL Activities t1SBDUJTFTJNQMFQBSBMMFMWFDUPSBEEJUJPO t$POTUSVDUQBSBMMFMPHSBNTUPTPMWFTJNQMFWFDUPSBEEJUJPOT t1SBDUJTFUSJHPOPNFUSZBOE1ZUIBHPSBTTUIFPSFNDBMDVMBUJPOT t3FTPMWFWFDUPSTJOUPUXPDPNQPOFOUT t.BUIFNBUJDBMMZTPMWFQSPCMFNTJOWPMWJOHUXPWFDUPSTBUEJFSFOUBOHMFT Grade 9 19 6OJU7FDUPST Resources http://www.physicsclassroom.com/class/vectors/u31b.cfm http://www.onlinemathlearning.com/pythagorean-theorem.html http://www.mathabout.com/od/geometrl/ss.Pythagorean.htm http://www.zonelandeducation.com (Physics Department, Mechanics, Vectors, Finding components, Visualising components, Component method of adding vectors http://www.physicsclassroom.com/class/vectors/U3LIf.cfm Where next? Adding vectors does not really get much more complex than this, at least not until proper vector notation has been covered. is is beyond the scope of this course. Some examples can be made more complex by providing angles other than the ones needed to calculate the components. Answers to review questions 1. a) 20 N le b) 50 N le c) 20 N down 2. Correct parallelogram diagram. Mathematically: 103 m/s at a bearing of 14°. 3. 181 N at 61° to the horizontal (right). 5IJTTFDUJPO TIPVME 4PNFBQQMJDBUJPOTPGWFDUPST GJMMBQQSPYJNBUFMZ 2 periods of Learning competencies UFBDIJOHUJNF #ZUIFFOEPGUIJTTFDUJPOTUVEFOUTTIPVMECFBCMFUP v %FGJOFUIFUFSNFRVJMJCSJVN v &YQMBJOUIFJNQPSUBODFPGGPSNJOHBUSJBOHMFPGUISFFWFDUPST v $BSSZPVUTPNFFYQFSJNFOUTUPJOWFTUJHBUFWFDUPST Starting off Most applications would have been covered through examples used in the previous sections. is section concentrates on the idea of forces in equilibrium. Students should be given the opportunity to test the theories experimentally. Teaching notes Explain the idea of balanced forces and relate this to situations where there are no resultant forces. Get two students of similar strength to push against each other (without moving). Discuss the forces and use simple diagrams to show that the 20 Grade 9 6OJU7FDUPST forces are in equilibrium. Discuss another 1-D example, perhaps a book resting on a desk. Ask the students to draw the forces acting on the book (remind them of the importance of scale). Extend this into 2-D but limit this to forces in the x direction (horizontal) and the y direction (vertical). Explain the Did you know? comment in the Students’ Book. Did you know? When in equilibrium all the horizontal forces (those in the x direction) must add up to equal zero. is can be written as: F x =0 means ‘sum of ’. So this literally means: the sum of all the forces in the x direction is zero. e same is true for the vertical forces (those in the y direction). is can be written as: F y =0 Give a few simple examples, ensuring that the forces in each direction add up to zero. Relate this back to equilibrium; stress that if in equilibrium the forces in each direction must add up to zero, giving no resultant force. Introduce the idea of scale diagrams for forces at dierent angles. Stress the importance of the two steps: t4FMFDUBTDBMFGPSZPVSGPSDFT t%SBXUIFNUPTDBMFPOFBFSUIFPUIFSJOBOZPSEFSMJOJOHUIFNVQIFBEUP tail, ensuring the directions are correct. Give a couple of examples showing that when the forces end up back at the start, they are in equilibrium. Get the students to draw several scale diagrams to check if the forces are in equilibrium. Discuss that the forces can be drawn in any order: the resultant will always be the same. Ask students to draw scale diagrams for three vectors and discuss the shape (triangle). Extend this by demonstrating how you can show equilibrium mathematically by resolving forces and then adding up the components. is can be quite tricky but provides good revision of most of the ideas covered in this unit. Activity 1.5: Answer Additionally, use force meters to experimentally check equilibrium. is can be 4UVEFOUThPXO completed working in small groups or by determining the weight of an unknownresults mass hanging on two strings. Activities t%SBXTDBMFEJBHSBNT t1SBDUJTFNBUIFNBUJDBMEFUFSNJOBUJPOPGFRVJMJCSJVN t1SBDUJTFFYQFSJNFOUBMWFSJDBUJPOPGFRVJMJCSJVN Resources http://www.physicsclassroom.com/class/vectors/u313c.cfm Grade 9 21 6OJU7FDUPST SA = starter activity MA = main activity CA = concluding activity Combining vectors SA %JTDVTTRVFTUJPO8IZTIPVMEUIFSFCFOPSFTVMUBOUGPSDFPOBCSJEHFPSBCVJMEJO MA 4UVEFOUTEJTDVTTNFBOJOHPGFRVJMJCSJVNBOEESBXTDBMFEJBHSBNTUPTPMWFFY FRVJMJCSJVN CA 3FWJFXRVFTUJPOT¦ Investigating vectors SA %JTDVTTJPOBDUJWJUZPOQBHFPG4UVEFOUTh#PPL MA "DUJWJUZ CA &OEPGVOJURVFTUJPOT¦ Where next? is topic is extended by the use of more complex examples and the use of simultaneous equations to determine equilibrium. Answers to review questions 1. ere is no resultant force acting on an object. 2. Any three examples drawn carefully to scale. 3. 1791 N (1800 N to 2 s.f.) Answers to end of unit questions 1.Scalar has magnitude only; vector has magnitude and direction. Examples: (scalar) distance, speed, mass, energy; (vector) displacement, velocity, acceleration, force, etc. 2. Scalars: distance, mass, time, volume, density, speed, temperature and energy; vectors: weight, velocity, acceleration and force. directed at 40° east of North. 3. D rawing of vector magnitude 40 m/s 4. 5 .8 km at 59° E of N 5. 26.8 N at 63° to the 12 N force 6. 15 km/h away from A 7. 100 N 22 Grade 9 Motion in a straight line Unit 2 This unit should GJMMBQQSPYJNBUFMZ By the end of this unit students should be able to: 12 periods of t %FTDSJCFUIFDIBSBDUFSJTUJDTPGVOJGPSNNPUJPO UFBDIJOHUJNF t %FGJOFUIFUFSNTEJTUBODFEJTQMBDFNFOUTQFFEBOEWFMPDJUZ Learning Competencies for Unit 2 t &YQMBJOUIFEJGGFSFODFCFUXFFOEJTUBODFBOEEJTQMBDFNFOU t %JTUJOHVJTICFUXFFOBWFSBHFBOEJOTUBOUBOFPVTTQFFETBOEWFMPDJUJFT t %FGJOFPGUIFUFSNBDDFMFSBUJPO t %FTDSJCFUIFNFBOJOHPGUIFUFSNVOJGPSNMZBDDFMFSBUFENPUJPO 2 t &YQMBJOUIFNFBOJOHPGUIFVOJU NT t 6TFWFMPDJUZoUJNFHSBQITUPEFUFSNJOFUIFBDDFMFSBUJPOPGBOPCKFDU t %FTDSJCFUIFLFZGFBUVSFTPGEJTUBODFoUJNFBOEEJTQMBDFNFOUoUJNFHSBQIT t 6TFEJTQMBDFNFOUoUJNFHSBQITUPEFUFSNJOFUIFWFMPDJUZPGBOPCKFDU t %FTDSJCFUIFLFZGFBUVSFTPGWFMPDJUZoUJNFHSBQIT t 6TFWFMPDJUZoUJNFHSBQITUPEFUFSNJOFUIFBDDFMFSBUJPOPGBOPCKFDUBOE UIFEJTQMBDFNFOU t %FTDSJCFUIFFRVBUJPOTPGVOJGPSNMZBDDFMFSBUFENPUJPO t 6TFUIFTFFRVBUJPOTUPTPMWFQSPCMFNT t &YQMBJOUIFJNQPSUBODFPGVTJOHUIFDPSSFDUTJHODPOWFOUJPOPS¦ XIFOEFBMJOHXJUIWFMPDJUJFTBOEBDDFMFSBUJPOT t %FGJOFUIFNFBOJOHPGUIFUFSNGSFFGBMM t "QQMZUIFFRVBUJPOTUPTPMWFQSPCMFNTSFMBUJOHUPGSFFGBMM t &YQMBJOUIFNFBOJOHPGUIFUFSNSFGFSFODFQPJOUPSSFGFSFODFGSBNF t %FTDSJCFUIFSFMBUJWFWFMPDJUJFTPGPCKFDUT t $BMDVMBUFUIFSFMBUJWFWFMPDJUZPGBCPEZXJUISFTQFDUUPBOPUIFSCPEZ XIFONPWJOHJOUIFTBNFPSJOUIFPQQPTJUFEJSFDUJPO 6OJGPSNNPUJPO Learning Competencies 5IJTTFDUJPO TIPVME GJMMBQQSPYJNBUFMZ 2 periods of UFBDIJOHUJNF #ZUIFFOEPGUIJTTFDUJPOTUVEFOUTTIPVMECFBCMFUP t %FTDSJCFUIFDIBSBDUFSJTUJDTPGVOJGPSNNPUJPO t %FGJOFUIFUFSNTEJTUBODFEJTQMBDFNFOUTQFFEBOEWFMPDJUZ t &YQMBJOUIFEJGGFSFODFCFUXFFOEJTUBODFBOEEJTQMBDFNFOU t %JTUJOHVJTICFUXFFOBWFSBHFBOEJOTUBOUBOFPVTTQFFETBOEWFMPDJUJFT Grade 9 23 6OJU.PUJPOJOBTUSBJHIUMJOF Starting off is topic deals with uniform motion in a more comprehensive way than previously studied. e key points to cover are the dierence between distance and displacement, and also speed and velocity. Additionally students should start thinking about average velocity and instantaneous velocity. Experimental work may be quite limited in this section, depending on resources. Teaching notes It is worth spending a short time discussing the idea of uniform motion. is leads into an explanation of the dierence between distance and displacement. Stress that displacement is a vector and so subject to all the rules covered in the previous topic. Give a simple example of a resultant displacement if a person walks 10 m North then 8 m East. Highlight the dierences between distance and displacement by using volunteers to walk around a pre-made course (ideally with a travel wheel to measure distance; alternatively they can try to take 0.5 m long steps). Extend this to include examples of circular motion. Aer one complete lap the distance may be 20 m but the displacement is zero, as the person is back at the start. Students could construct scale diagrams (this time for displacement vectors) to determine total distance travelled and resultant displacement for various examples. Issue students with maps and get them to plan simple routes from one town to another. Ask them to determine the distance and displacement (not forgetting the angle or bearing) in each case. is could be extended to include much longer journeys from one continent to another. Revise the idea of speed and explain the concept of velocity. Stress the term average in each case and give the students plenty of examples to calculate average speeds and average velocities (including a direction). ey could use their previous scale diagrams or just simple statements written on the board. is could be extended to include circular motion and the use of 2r to determine the distance travelled. Students could make their own courses and calculate dierent average speeds and average velocities for dierent methods of completing the course (crawling, running, etc). Activity 2.1: Answers 4UVEFOUThPXO BOTXFST Activity 2.2: Answer 4UVEFOUThPXO BOTXFST 24 When they are happy with the calculations and dierences between the key terms, discuss the idea of average speed. What does it mean? Give examples of longer journeys, such as their journey to school. At dierent times they would have been travelling at dierent speeds. Use this idea to introduce the concept of instantaneous speed and instantaneous velocity. Keep it as speed or velocity at any given time; there is no need for any calculus at this stage. Use the limitations of average speed and average velocity to lead into the necessity to elicit more information from a journey; one way to do this is via a motion graph. In this case we can plot graphs of distance or displacement against time. Sketch a simple displacement–time graph showing a straight line through the origin, which then goes at for a few seconds. Ask the students to discuss the motion of the object. Graphical representation will be covered in more detail later. Grade 9 6OJU.PUJPOJOBTUSBJHIUMJOF SA = starter activity MA = main activity CA = concluding activity What is uniform motion? SA %JTDVTTNFBOJOHPGVOJGPSNNPUJPOBOEWFDUPSOBUVSFPGEJTQMBDFNFOU MA "DUJWJUZBOEEJTDVTTJPOBDUJWJUZ CA 3FWJFXRVFTUJPO Average and instantaneous speed and velocity SA %JTDVTTBCVTKPVSOFZBTEFTDSJCFEPOQBHFPGUIF4UVEFOUTh#PPLUPIJHIMJHIUUIF EJGGFSFODFTCFUXFFOBWFSBHFBOEJOTUBOUBOFPVT MA "DUJWJUZ CA 4UVEFOUTFYQMBJOEJGGFSFODFCFUXFFOBWFSBHFBOEJOTUBOUBOFPVTUPBQBSU EJTUBODF¦UJNFHSBQIPGUIFJSKPVSOFZUPTDIPPM3FWJFXRVFTUJPO Activities t$POTJEFSEJFSFODFTCFUXFFOEJTUBODFBOEEJTQMBDFNFOUPOTJNQMFKPVSOFZT t1SBDUJTFDBMDVMBUJPOTPGBWFSBHFTQFFEBOEBWFSBHFWFMPDJUZ Resources http://www.physicsclassroom.com/class/idkin/u1l1d.cfm Where next? 1SPQFSEFOJUJPOTPGWFMPDJUZXJMMCFDPWFSFEMBUFSJOUIFDPVSTFJTXJMMJODMVEF a simple introduction to calculus and its importance when dealing with motion. Most moving bodies speed up or slow down during their motion. e concept of acceleration and deceleration will be covered in the next section. Answers to review questions 1. Distance is a scalar and has only size. Displacement is a vector quantity and so has a direction as well as size. 2. 29.9 km/s 3. a) 20 km b) 9.3 km/h (2.6 m/s) c) 6.7 km/h (1.9 m/s) direction N 53 E Grade 9 25 6OJU.PUJPOJOBTUSBJHIUMJOF 5IJTTFDUJPO TIPVME 6OJGPSNMZBDDFMFSBUFENPUJPO GJMMBQQSPYJNBUFMZ 2 periods of Learning Competencies UFBDIJOHUJNF #ZUIFFOEPGUIJTTFDUJPOTUVEFOUTTIPVMECFBCMFUP t %FGJOFUIFUFSNBDDFMFSBUJPO t %FTDSJCFUIFNFBOJOHPGUIFUFSNVOJGPSNMZBDDFMFSBUFENPUJPO 2 t &YQMBJOUIFNFBOJOHPGUIFVOJU NT t 6TFWFMPDJUZoUJNFHSBQITUPEFUFSNJOFUIFBDDFMFSBUJPOPGBOPC Starting off is section builds on the correct description of velocity to develop the students’ VOEFSTUBOEJOHPGBDDFMFSBUJPO$BSFTIPVMECFUBLFOXIFOEFTDSJCJO and its units. Teaching notes Begin by asking the students what they understand by the term acceleration. Most XJMMDPNNFOUPOTQFFEJOHVQPSPCKFDUTHFUUJOHGBTUFS(JWFUIFNUIF It is important to note that acceleration is a change in velocity not a change in speed. A change in velocity might be: t(FUUJOHGBTUFS t(FUUJOHTMPXFS t$IBOHJOHEJSFDUJPO Ask the students to think of examples in which the speed of an object is constant but its velocity is changing. is distinction is very important when it comes to looking at forces and acceleration. Discuss the units of acceleration and what they actually mean. Give some examples. is will help them realise the dierence between acceleration and velocity. e two are oen confused, especially when describing the motion of an accelerated object. When athletes such as Kenenisa Bekele and Tirunesh Dibaba are running, there BSFFYBNQMFTPGUIFNJODSFBTJOHUIFJSWFMPDJUZBUTUBSUBOEUPXBSE line), accelerating at constant speed (as they go round the bends) and decreasing UIFJSWFMPDJUZBFSOJTIJOH"MMPGUIFTFBSFFYBNQMFTPGBDDFMFSBUJP Students should practise some acceleration calculations, including determining DIBOHFJOWFMPDJUZJOJUJBMWFMPDJUZBOEOBMWFMPDJUZ To start velocity–time graphs you could sketch a graph on the board but fail to label the y-axis and ask the students what kind of motion it represents. Most will assume it is a displacement–time graph. Stress the importance of labelling the axes. 26 Grade 9 6OJU.PUJPOJOBTUSBJHIUMJOF SA = starter activity MA = main activity CA = concluding activity What is acceleration? SA 4UVEFOUTEJTDVTTXIBUUIFZVOEFSTUBOECZABDDFMFSBUJPOJOHSPVQTCFGPSFZPV DPSSFDUTDJFOUJGJDEFGJOJUJPO MA 8PSLJOHSPVQTUPUIJOLPGFYBNQMFTXIFSFTQFFEJTDPOTUBOUCVUWFMPDJUZJTDIB %JTDVTTVOJUTPGBDDFMFSBUJPO3FTFBSDIBUIMFUFTBDDFMFSBUJPOJOBSBDFJOD BDDFMFSBUJPOBUUIFFOE CA %JTDVTTUIFRVFTUJPOA8IZJTUIF&BSUIBDDFMFSBUJOHJOJUTPSCJU 'JHVSFJO4UVEFOUT Acceleration calculations SA "TLTUVEFOUTUPXPSLJOQBJSTUPSFBSSBOHFUIFBDDFMFSBUJPOFRVBUJPOUPNBLFD TQFFEBOEUJNFUIFTVCKFDUPGUIFFRVBUJPO MA 4UVEFOUTUBDLMFFYBNQMFTPGBDDFMFSBUJPODBMDVMBUJPOT.PSFBCMFTUVEFOU UIFJSPXOQSPCMFNTGPSBQBSUOFSUPTPMWFUIFZNVTUPGDPVSTFXPSLPVUUIFBOTX UIFZDBODIFDLJU CA 3FWJFXRVFTUJPOT¦%SBXHSBQIUPTIPXNPUJPOPGDBSJORVFTUJPOWFMPDJUZ¦UJNF BOELFFQGPSOFYUMFTTPO Activities t$POTJEFSFYBNQMFTPGBDDFMFSBUJPO t1SBDUJTFDBMDVMBUJPOTPGBDDFMFSBUJPOBOEEFDFMFSBUJPO Resources www.gcsescience.com/pfm37.htm http://see.msfc.nasa.gov/sparkman/section_docs/appendix_c.htm Where next? e next section looks into distance–time, displacement–time and velocity–time graphs. is includes sketching velocity–time graphs from information collected from displacement-time graphs. If you have more able students they could also start to determine the instantaneous acceleration by taking tangents of the line to determine the gradient and hence the acceleration at that point. Answers to review questions "DDFMFSBUJPOJTEFOFEBTUIFSBUFPGDIBOHFPGWFMPDJUZBOEJTNFBTVSFEJO m/s2. 2. 3 m/s2 3. 400 m/s Grade 9 27 6OJU.PUJPOJOBTUSBJHIUMJOF 5IJTTFDUJPO TIPVME (SBQIJDBMEFTDSJQUJPOPGVOJGPSNMZBDDFMFSBUFENP GJMMBQQSPYJNBUFMZ 2 periods of Learning Competencies UFBDIJOHUJNF #ZUIFFOEPGUIJTTFDUJPOTUVEFOUTTIPVMECFBCMFUP t %FTDSJCFUIFLFZGFBUVSFTPGEJTUBODFoUJNFBOEEJTQMBDFNFOUoU t 6TFEJTQMBDFNFOUoUJNFHSBQITUPEFUFSNJOFUIFWFMPDJUZPGBOPC t %FTDSJCFUIFLFZGFBUVSFTPGWFMPDJUZoUJNFHSBQIT t 6TFWFMPDJUZoUJNFHSBQITUPEFUFSNJOFUIFBDDFMFSBUJPOPGBOPC UIFEJTQMBDFNFOU Starting off Simple motion graphs may be drawn using data collected with nothing more than a metre rule (or measuring tape or travel wheel) and a stopwatch. Alternatively ticker tapes, timers or light gates could be used where available. Activity 2.3: Answer Teaching notes Ask students to sketch the shape of simple displacement–time graphs, perhaps Students should QSPEVDFBHSBQI including: TIPXJOHBTFSJFTPG $POTUBOUWFMPDJUZ lines and be able UPEFTDSJCFXIBU $POTUBOUWFMPDJUZCVUGBTUFSUIBOHSBQI FBDIMJOFNFBOT $POTUBOUWFMPDJUZTMPXFSUIBOHSBQIUIFOTUPQTUIFOUIFTBNFDPOTU in relation to their velocity as graph 1. KPVSOFZUPTDIPPMo 4. Accelerating from rest. DPNNFOUTTVDIBT $POTUBOUWFMPDJUZUIFTBNFBTHSBQIUIFOHSBEVBMMZTMPXJOHEPXOU XBMLJOHBUDPOTUBOU TQFFEUPGSJFOEhT $POTUBOUWFMPDJUZUIFTBNFBTHSBQIUIFOTUPQQFEUIFOIFBEJOHCBDLU IPVTFXBJUJOHGPS start at the same velocity. GSJFOESVOOJOH Review each of these with the class, concentrating on linking the gradient of the BUGBTUFSTQFFEUP DBUDICVTXBJUJOHline to the velocity. e steeper the line, the faster the velocity. Stress the negative gradient and what this means (negative velocity means travelling in the opposite GPSCVT direction). Spend time discussing what it means if a line is curved. Students will not be plotting curved lines, but it is worth ensuring they understand qualitatively what they represent. Students could sketch distance–time graphs for various journeys (for example their journey to school). Show simple calculations using a sample plotted displacement–time graph. Explain how the displacement for a particular section and the time taken can be found. Once students are happy with the key ideas they should plot a couple of example displacement–time graphs; these should include a range of gradients (including zero and negative values). Each section should be a straight line; there is no need to extend to accelerating/decelerating quantitatively at this stage. 28 Grade 9 6OJU.PUJPOJOBTUSBJHIUMJOF Ask them to describe each section and calculate the average velocity for each section. is could be turned into a practical activity if a 100 m course is laid out into 10 m sections. Students working in groups can walk, run or jog through the 100 m as other members of the group time how long they take to complete each 10 m section. Activity 2.4: Answer 30 28 26 24 Velocity (m/s) 22 20 acceleration = 24 6 20 = 0.9 m/s 2 18 16 14 12 10 8 6 4 2 deceleration = 24 0 8 = 3 m/s 2 distance = (440 x 6) + (10 x 18) + (120 x 18) + (4 x 24) ± 5076 m = 5.1 km 0 0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 400 420 440 460 480 500 Time (s) &YQMBJOUPUIFNIPXUPOEUIFBWFSBHFWFMPDJUZUPUBMEJTQMBDFNFOUUJNFUBLFO ey can calculate the average velocities up to certain times using their graphs. Discuss how instantaneous velocities can be calculated by determining the gradient at that point (as the graphs will contain a series of straight sections, tangents will not be necessary at this stage). rough examples or discussion, explain the dierences between distance–time and displacement–time graphs (there is a good example in the Students’ Book). is also acts as a nice summary of distance, displacement, speed and velocity. At the end of the last section, you may have sketched a graph on the board but failed to label the y-axis. Most of the students will have assumed it is a displacement–time graph. Stress the importance of labelling the axes and then get students to sketch several velocity–time graphs. For example: t$POTUBOUWFMPDJUZ t$POTUBOUWFMPDJUZCVUGBTUFSUIBOHSBQI t"DDFMFSBUJOHGSPNSFTU t$POTUBOUWFMPDJUZUIFTBNFBTHSBQIUIFOHSBEVBMMZTMPXJOHEPXOUPBTUPQ As with displacement–time graphs, take time to explain the key features of the graph. At this stage, concentrate on the gradient of the line and what it represents (acceleration). Go on to explain that the area under the line represents the displacement. Grade 9 29 6OJU.PUJPOJOBTUSBJHIUMJOF SA = starter activity MA = main activity CA = concluding activity Motion graphs SA %JTDVTTHSBQIPGKPVSOFZUPTDIPPMESBXOJOMFTTPOPGTFDUJPOXJUIQBSUOFS MA "DUJWJUZBOEBDUJWJUZEFTDSJCFEPOQBHFPGUIJTCPPL CA 4UVEFOUTXPSLXJUIBQBSUOFSBOEUFMMBATUPSZUPGJUHSBQITJO'JHVSFJO4UVEFOU BOEUIFOGFFECBDLJEFBTUPSFTUPGDMBTT Velocitytime graphs SA "TLTUVEFOUTUPFYQMBJO'JHVSFJO4UVEFOUTh#PPL MA CA "DUJWJUZ 3FWJFXRVFTUJPOT¦ Activities t1SBDUJTFDPOTUSVDUJPOPGEJTUBODFoUJNFBOEEJTQMBDFNFOUoUJN including both simple sketches and accurate plots. t6TFHJWFOEBUBUPQMPUTFWFSBMWFMPDJUZoUJNFHSBQIT t6TFHSBQITUPEFUFSNJOFBDDFMFSBUJPOBOEEJTQMBDFNFOU t1SPWJEFFYBNQMFTPGOFHBUJWFWFMPDJUJFT Resources http://www.physics.mclarenhigh.com/Flash/MotionDiagram.html Where next? FOFYUTFDUJPOMPPLTBUTPMWJOHQSPCMFNTBCPVUVOJGPSNNPUJPOVT FRVBUJPOTPGNPUJPO*GBOZUISFFRVBOUJUJFTGSPNJOJUJBMWFMPDJUZ acceleration, displacement and time are known, the equations of motion allow the other two to be calculated. Answers to review questions 1. a) 0 s – 20 s constant velocity 2 m/s 20 s – 30 s stationary 30 s – 40 s constant velocity 4 m/s 40 s – 50 s stationary 50 s – 70 s constant velocity 2 m/s back towards start 70 s – 80 s constant velocity 4 m/s ending back at start b) 4 m/s c) 1.78 m/s d) 0 m/s 30 Grade 9 6OJU.PUJPOJOBTUSBJHIUMJOF 2 m/s 2. a) 0 s – 8 s constant acceleration from rest 0.25 8 s – 10 s constant velocity 22 m/ 10 s – 14 s constant acceleration 12 m/s 14 s – 16 s constant deceleration 22 m/s 16 s – 18 s constant deceleration 12 m/s to rest b) 0.25 m/s2 c) 2 m/s2 d) i) 8 m ii) 38 m e) 6 m/s &RVBUJPOTPGVOJGPSNMZBDDFMFSBUFENPUJPO Learning Competencies 5IJTTFDUJPO TIPVME GJMMBQQSPYJNBUFMZ 4 periods of UFBDIJOHUJNF #ZUIFFOEPGUIJTTFDUJPOTUVEFOUTTIPVMECFBCMFUP t %FTDSJCFUIFFRVBUJPOTPGVOJGPSNMZBDDFMFSBUFENPUJPO t 6TFUIFTFFRVBUJPOTUPTPMWFQSPCMFNT t &YQMBJOUIFJNQPSUBODFPGVTJOHUIFDPSSFDUTJHODPOWFOUJPOPSo XIFOEFBMJOHXJUIWFMPDJUJFTBOEBDDFMFSBUJPOT t %FGJOFUIFNFBOJOHPGUIFUFSNGSFFGBMM t "QQMZUIFFRVBUJPOTUPTPMWFQSPCMFNTSFMBUJOHUPGSFFGBMM Starting off is section builds on an understanding of what is meant by uniform acceleration BOEBWFSBHFWFMPDJUZUPQSPEVDFWFFRVBUJPOTPGNPUJPO Teaching notes Ask students to explain what is meant by the terms uniform acceleration and average velocity. Introduce the symbols s – displacement u – initial velocity voOBMWFMPDJUZ a – acceleration t – time Mention the use of the Greek symbol delta as an abbreviation for 'change in' but do not proceed any further with calculus at this stage. Grade 9 31 6OJU.PUJPOJOBTUSBJHIUMJOF Activity 2.5: Answer 'PSTVCTUJUVUF for vGSPNJOUP s›uuatt s›uatt 2 s›utat 4UVEFOUTXJMMQSPCBCMZOFFEUPCFHJWFOIJOUTBTUPIPXUPOEFRVBUJP Equation (5) should be easy as the method is the same as for equation (3). s = ut + ½at2 'PSTRVBSF v2uat 2 v2 = u2 uata v2 = u2 a ½at2 6TFUIFTZNCPMTUPEFSJWFUIFSTUUXPFRVBUJPOTPGNPUJPO velocity change = v – u a = (v – u) / t rearrange equation to form equation (1) v = u + at average velocity for an object which accelerates uniformly = ½(u + v) ½(u + v) = s/t rearrange equation to form equation (2) s = ½(u+v)t 2t 2 ut v2 = u2 + 2as 'PSTVCTUJUVUF GPSVGSPN JOUP s›voatvt s›voatt s›vtoat s = vt– ½at2 2 Show the students some examples using the equations. e completion of a table is a good way of ensuring students write down the quantities they know, and the gaps in the table clearly show what is still to be calculated. is will also make sure they choose the correct equation. Ask students to draw a simple velocity–time graph for a body accelerating from an initial velocity uUPBOBMWFMPDJUZv in a time t. ey should then calculate the area between the graph and the time axis. is is commonly referred to as the area under the graph and involves adding the area of a rectangle to the area of a triangle. Substituting for v in the equation for the area of the triangle will generate the equation s = ut + ½at2. Reinforce the fact that velocity and acceleration are both vectors. Ask one student to walk with a velocity of 2 m/s and a second student to walk with a velocity of oNTFOBTLUIFSTUUPIBWFBOFHBUJWFBDDFMFSBUJPOBOEUIFTFDPOEUPIB QPTJUJWFBDDFMFSBUJPOFZTIPVMETUBSUCZXBMLJOHJOPQQPTJUFEJSF should slow down and the second should speed up. row a ball into the air. Ask students in which direction the ball is accelerating. ere is a negative acceleration vertically upwards as the ball slows down. is means the ball is falling towards the Earth even as it moves upwards. If there is no air resistance, the ball is falling freely. Because the Earth is not a perfect sphere, the acceleration due to gravity varies 2 and with latitude. At the equator, the acceleration due to gravity is 9.780 m/sat 2 . Addis Ababa is close to the equator and the acceleration the poles it is 9.832m/s 2. due to gravity there is 9.782 m/s 32 Grade 9 6OJU.PUJPOJOBTUSBJHIUMJOF SA = starter activity MA = main activity CA = concluding activity Equations of uniform acceleration SA "TLTUVEFOUTUPFYQMBJOUIFUFSNTAVOJGPSNBDDFMFSBUJPOBOEABWFSBHFWFMP MA "DUJWJUZ CA 4UVEFOUTDSFBUFQPTUFSUPTIPXFRVBUJPOTPGNPUJPO Using the equations SA 8PSLUISPVHIFYBNQMFTPOQBHFPG4UVEFOUTh#PPLBTLJOHTUVEFOUTUPUFMMZPVO MA 4UVEFOUTUPUBDLMFFYBNQMFTUIBUSFRVJSFUIFNUPVTFUIFFRVBUJPOT$IFDLQSPHS XBMLJOHSPVOESPPNBOEBTTFTTJOHIPXTUVEFOUTBSFHFUUJOHPO CA 3FWJFXRVFTUJPOT¦ Velocitytime graphs SA "TLTUVEFOUTUPESBXTJNQMFWFMPDJUZ¦UJNFHSBQITFFQBHFPGUIJTCPPL%JTDVTTI EFSJWFs = ut›at 2 MA %JTDVTTBDDFMFSBUJPOEVFUPHSBWJUZBOEMFUTUVEFOUTFYQFSJNFOUXJUIUIJTD TNBMMCBMMZPVNBZXBOUUPEPUIJTPVUTJEF CA 3FWJFXRVFTUJPO Free fall SA *GZPVESPQQFEBTUPOFBOEBGFBUIFSGSPNUIFTBNFIFJHIUXIJDIXPVMEMBOEGJSTU 8 %JTDVTTJOTNBMMHSPVQTBOEGFFECBDLJEFBT MA "DUJWJUZ CA 8IZNJHIUFYQFSJNFOUBMBOEUIFPSFUJDBMSFTVMUTEJGGFS %JTDVTTJOTNBMMHSP RVFTUJPOT¦ Activities Activity 2.6: Answer 4UVEFOUT NBZGJOE t6TFFRVBUJPOTPGNPUJPOUPTPMWFQSPCMFNTXIFSFUISFFPGUIFWF RVBOUJUJFT s, UIBUUIFPSFUJDBM BOE u, v, a, t are known. FYQFSJNFOUBM SFTVMUT t%SPQCBMMTGSPNBWBSJFUZPGIFJHIUTBOEUJNFIPXMPOHUIFZUBLF UPSFBDIUIF EJGGFS CFDBVTF ground. Emphasise that repeated readings improve the reliability of results. B NFBTVSFNFOUT Use the results to calculate the acceleration due to gravity. BSF OFWFS UPUBMMZ t$PNQBSFFYQFSJNFOUBMSFTVMUTXJUIUIFPSFUJDBMMZDBMDVMBUFE SFTVMUT BDDVSBUF C UIFUIFPSZ BTTVNFT OPBJS Resources SFTJTUBODFUP http://hyperphysics.phy-astr.gsu.edu/hbase/mot.html NPUJPO Where next? e next section looks at how a frame of reference allows a comparison to be made between two moving objects. Grade 9 33 6OJU.PUJPOJOBTUSBJHIUMJOF Answers to review questions 1. v = u + at s = ½(u + v)t s = ut + ½at2 v2 = u2 + 2as s = vt– ½ at2 2. a) 42 m 2 b) 2.67 m/s 3. 5.25 m/s 4. 138 m 5. An object falling freely is being pulled towards the centre of the Earth because of gravity. 5IJTTFDUJPO TIPVME 3FMBUJWFWFMPDJUZJOPOFEJNFOTJPO GJMMBQQSPYJNBUFMZ 2 periods of Learning Competencies UFBDIJOHUJNF #ZUIFFOEPGUIJTTFDUJPOTUVEFOUTTIPVMECFBCMFUP t &YQMBJOUIFNFBOJOHPGUIFUFSNSFGFSFODFGSBNFPSSFGFSFODFQP t %FTDSJCFUIFSFMBUJWFWFMPDJUJFTPGPCKFDUT t $BMDVMBUFUIFSFMBUJWFWFMPDJUZPGBCPEZXJUISFTQFDUUPBOPUIF XIFONPWJOHJOUIFTBNFPSJOUIFPQQPTJUFEJSFDUJPO Activity 2.7: Answers Starting off is section introduces the idea of a frame of reference. When we describe a 3FMBUJWFWFMPDJUJFT moving object, we usually describe it from our own point of view. is is known of: as our frame of reference. CPZUPESJWFS LNI HJSMUPESJWFS Teaching notes oLNI Begin by asking the students to point to the right. ey will all point to their CPZUPHJSMLNI right. If you are facing them, then your right is their le. Since you are giving the CPZUPQBTTFOHFS instruction it is your frame of reference that is the default so they should all have LNI pointed to their le. HJSMUPQBTTFOHFS Arrange the students in a square, facing inwards. Ask one student to walk from LNI the mid point of one side to the mid point of the opposite side. Ask the students ESJWFSUPQBTTFOHFS to describe the motion of their friend. For some, the student will be walking away; LNI for others they will be walking towards; for a third group the movement will be GSPNMFUPSJHIUBOEGPSUIFOBMHSPVQJUXJMMCFSJHIUUPMFFSFBSFGPV dierent frames of reference for the observers. A passenger is on a train travelling at a constant velocity of 30 m/s. He throws a ball vertically in the air. It returns to his hand 0.5 s later. As far as he is concerned, the ball goes straight up and down. But, to someone on the platform watching the 34 Grade 9 6OJU.PUJPOJOBTUSBJHIUMJOF train as it goes through the station, the ball follows a parabolic path landing 15 m further forward from the point at which it was thrown upwards. ere are two dierent frames of reference. e laws of physics apply if the frame of reference is stationary or moving with constant velocity. ese frames of reference are known as inertial frames of reference. What would happen to the ball in the train if the train braked just aer the passenger had thrown the ball into the air? It would land in front of him. e general rule for relative velocities is to add the two velocities when the bodies are moving in opposite directions towards each other and to subtract when moving in the same direction. SA = starter activity MA = main activity CA = concluding activity Relative velocity (1) SA "SSBOHFTUVEFOUTJOTRVBSFBOEDBSSZPVUBDUJWJUZPOQBHF MA %JTDVTTFYBNQMFPGQBTTFOHFSPOUSBJOUISPXJOHBCBMMBOEXIBUPCTFSWFSPOQ TFFBCPWF CA *OTNBMMHSPVQTFYQMPSFSFMBUJWFNPUJPOPGWFIJDMFTVTJOHUPZUSBJOTPSDBS *OTNBMMHSPVQTMJTUFYBNQMFTPGSFMBUJWFNPUJPOJOFWFSZEBZMJGF Relative velocity (2) SA 5IJOLBCPVUUIJTVTJOH4UVEFOUTh#PPLQBHF MA CA "DUJWJUZ 3FWJFXRVFTUJPOT¦BOEFOEPGVOJURVFTUJPOT Activities t$BMDVMBUFSFMBUJWFWFMPDJUJFTGPSEJFSFOUTJUVBUJPOTGPSFYBNQMFPOFWFIJDMF overtaking another; two footballers both running towards the ball. t%JTDVTTXIZUIFTQFFEMJNJUTPOSPBETXJUIDFOUSBMCBSSJFSTBSFIJHIFSUIBOPO normal roads. Resources http://physicslearningsite.com/relative.html http://www.tutorvista.com/physics/relative-velocity-problems-and-answers Where next? JTUPQJDJTFYUFOEFECZFYBNJOJOHOPOMJOFBSNPUJPO1SPKFDUJMFTIBWF horizontal and vertical components of velocity and displacement. e equations of motion used in this unit are relevant in solving problems involving projectiles. Answers to review questions 1. A frame of reference is an object with respect to which we compare another object's position and motion. Grade 9 35 6OJU.PUJPOJOBTUSBJHIUMJOF 2. a) 5 m/s b) 6 m/s Answers to end of unit questions 1.3.75 hours 2. 360 m 3. 10 m/s2 HSBQI TIPXTJODSFBTJOH HSBEJFOU GPS UIFSTU TFDPOET UIFOTUSBJHIU MJOF NT 5. a) B – line parallel to time axis b) D – negative gradient c) A – steepest gradient 6. a) graph shows positive gradient for 20 seconds; horizontal line for 40 seconds; negative gradient for 20 seconds b) car is accelerating for 20 s from 16 m/s to 24 m/s; continues at uniform velocity of 24 m/s for 40 s; decelerates to 18 m/s for 20 s 2 c) 0.4 m/s2 ; –0.3 m/s 7. 27 m/s 8. a) 1 m/s2 b) 250 m c) 250 m 9. 64 m 10.3 s – 45 m ; 30 m/s 4 s – 80 m ; 40 m/s 11.30 m/s; vertically downwards 12.15 km/h 13.400 km/h 14.240 km/h 15. i) Displacement A C = (10 x 20)+(60 x 20)+(20 x 20) = 200+1200+400 = 1800 m ii) Displacement C Displacement A B = (5 x 10)+(30 x 10)+(5 x 10) = 50+300+50 = 400 m B = 2200 m 30 28 26 24 Velocity (m/s) 22 20 acceleration = 200 240 = 0.5 m/s 2 18 acceleration = 20 20 = 1 m/s 2 16 14 12 10 acceleration = 10 10 = 1 m/s 2 8 6 4 acceleration = 10 10 = 1 m/s 2 2 0 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 Time (s) 36 Grade 9 Force and Newton’s laws of motion Unit 3 This unit should GJMMBQQSPYJNBUFMZ By the end of this unit students should be able to: 19 periods of UFBDIJOH UJNF t -JTUTPNFPGUIFGPSDFTUIBUPDDVSJOOBUVSFBOEDBUFHPSJTFUIFN BT DPOUBDUPSOPODPOUBDU Learning Competencies for Unit 3 t 4UBUF/FXUPOTGJSTUMBX t &YQMBJOUIFSFMBUJPOTIJQCFUXFFONBTTBOEJOFSUJB t 4UBUF)PPLFTMBXBOEEJTUJOHVJTICFUXFFOFMBTUJDBOEJOFMBTUJDNBUFSJBMT t &YQFSJNFOUBMMZEFUFSNJOFBOEEFTDSJCFUIFGPSDFDPOTUBOUPGBTQSJOH t %JTUJOHVJTICFUXFFOSFTVMUBOUGPSDFBOEFRVJMJCSBOUGPSDF t %FTDSJCFUIFFGGFDUPGBGPSDFBDUJOHPOBCPEZ t "QQMZ/FXUPOTTFDPOEMBXnet BT=FmaUPTPMWFQSPCMFNT t 3FTPMWFGPSDFTJOUPSFDUBOHVMBSDPNQPOFOUTBOEDPNQPTFGPSDFTBDUJOHPO BCPEZVTJOHDPNQPOFOUNFUIPET t %FTDSJCFUIFUFSNXFJHIUBOEXFJHIUMFTTOFTTJODMVEJOHEJTUJOHVJTIJOH CFUXFFOXFJHIUBOEBQQBSFOUXFJHIU t $BMDVMBUFUIFXFJHIUBOEBQQBSFOUXFJHIUPGBOPCKFDUJOBSBOHFPG TJUVBUJPOT t &YQMBJOUIFDBVTFTPGGSJDUJPOBMGPSDFT t %FTDSJCFUIFEJGGFSFODFTCFUXFFOMJNJUJOHGSJDUJPOTUBUJDGSJDUJPOBOE LJOFUJDGSJDUJPO t %SBXGSFFCPEZEJBHSBNTGPSPCKFDUTPOJODMJOFEQMBOFTUPJODMVEF GSJDUJPOBMGPSDFTBOEVTFUIFTFEJBHSBNTUPTPMWFQSPCMFNT 'PSDFTJOOBUVSF Learning Competencies 5IJTTFDUJPO TIPVME GJMMBQQSPYJNBUFMZ 2 periods of UFBDIJOHUJNF #ZUIFFOEPGUIJTTFDUJPOTUVEFOUTTIPVMECFBCMFUP t -JTUTPNFPGUIFGPSDFTUIBUPDDVSJOOBUVSFBOEDBUFHPSJTFUIFNBT DPOUBDUPSOPODPOUBDU t 4UBUF/FXUPOTGJSTUMBX t &YQMBJOUIFSFMBUJPOTIJQCFUXFFONBTTBOEJOFSUJB t 4UBUF)PPLFTMBXBOEEJTUJOHVJTICFUXFFOFMBTUJDBOEJOFMBTUJDNBUFSJBMT t &YQFSJNFOUBMMZEFUFSNJOFBOEEFTDSJCFUIFGPSDFDPOTUBOUPGBTQSJOH Grade 9 37 6OJU'PSDFBOE/FXUPOTMBXTPGNPUJPO Starting off is topic deals with forces in a more comprehensive way than previously studied. ere are two areas of study – the nature of forces and elastic behaviour. It is advisable to spend one lesson on each. Students should be allowed to use springs in the second lesson to nd the spring constant from a graph. Activity 3.1: Answer Teaching notes $POUBDUGPSDFT Start by asking students to explain the term force. Most will recognise forces GSJDUJPOESBH as pushes and pulls. A simple description for a force is something that changes UISVTUVQUISVTU the motion or shape of an object. Allow the students to experiment with some UFOTJPOSFBDUJPOeveryday objects: tUVSOJOHBUBQ /PODPOUBDUGPSDFT FMFDUSPTUBUJD tVOTDSFXJOHBCPUUMF XFJHIUHSBWJUZ tQVMMJOHPQFOBESBXFS NBHOFUJTN tQVTIJOHBCPPLBDSPTTBCFODI tNBHOFUTBUUSBDUJOHBOESFQFMMJOH tIPMEJOHBDPSLBUUIFCPUUPNPGBUBOLPGXBUFS Activity 3.2: Answer tTRVFF[JOHBTQPOHF 4UVEFOUThPXO tUXJTUJOHBQJFDFPGNPEFMMJOHDMBZ results Explain the dierence between contact forces and non-contact forces. e idea of a non-contact force is more dicult to understand, so spend some time explaining this; use magnets as an example. It does not oen snow in Ethiopia and temperatures rarely fall below 0°C so many students will have no rst-hand knowledge of sliding on ice. A simple demonstration of an ice cube being given a push to start it moving across a table should help to show that no force is needed for something to keep moving. Force is needed to start it moving, slow it down or change its direction. is is Newton’s rst law of motion. You can demonstrate inertia in two ways. One fun way is to use a bucket of water. is is best done outside the classroom on a ne day! Half ll a bucket with water BOESVOBMPOHXJUIUIFCVDLFUHSBEVBMMZUJQQJOHJUJOUPUIFIPSJ[POU e water will stay in the bucket until you stop suddenly. e inertia of the water makes it continue to move forwards. Inertia is the reluctance of any moving object (the water) to stop moving. Secondly, ll a beaker with water. Place a foil dish on top of the beaker. Stand a tube of paper on top of the dish and balance an egg on the tube. Hold the beaker BOETUSJLFUIFEJTIIPSJ[POUBMMZFEJTIBOEUVCFXJMMNPWFIPSJ[POUBMM egg falls into the beaker. Inertia is also the reluctance of any stationary object to start moving. Activity 3.3: Answer 4UVEFOUThPXO results 38 It is best if students are allowed to stretch their own springs. Springs can be made using some wire wrapped around a piece of dowel or a large diameter pen or pencil. It is important to check beforehand how much load the springs will take before they stretch too far and will not return to their original length. Do not let the students add weights beyond this limit. Make sure that the loops at the top and bottom of the spring cannot unwind. If they do, weights might fall o and the springs might y o the support and hit someone. Grade 9 6OJU'PSDFBOE/FXUPOTMBXTPGNPUJPO e students will usually measure the length of the spring every time they add a weight. To nd the extension they will need to subtract the original length of the spring each time. e most common error when doing this experiment is to subtract the previous length. *UJTOPSNBM UPQMPU UIFRVBOUJUZ XF WBSZ POUIFxBYJTBOEUIFRVBOUJUZ XF NFBTVSF as a result on the y-axis. If we do this, then the graph will be extension against load (force). Conventionally, for this relationship we plot force against extension. Once the spring has been calibrated, it is possible to make a newtonmeter. Only aer the newtonmeter has been calibrated, allow the students to stretch their springs further – or, to save on springs, this can be done as a demonstration. e spring increases in length at a faster rate and will not return to its original length. e spring has deformed plastically. ere may be some confusion here, as many plastics do not deform plastically. SA = starter activity MA = main activity CA = concluding activity What are forces? SA "TLTUVEFOUTUPFYQMBJOUIFUFSNAGPSDF"MMPXUIFNUPFYQFSJNFOUXJUIFWFSZEB TFFQBHF MA "DUJWJUZBOE"DUJWJUZ CA "TLTUVEFOUTUPFYQMBJOSFTVMUTPG"DUJWJUZJOUFSNTPG/FXUPOTGJSTUMBXBOE Hooke’s law SA (JWFTUVEFOUTTPNFNPEFMMJOHDMBZBOEBMMPXUIFNUPFYQFSJNFOUXJUIUIFFGGF GPSDFTPOUIFDMBZ MA &YQFSJNFOUXJUITUSFUDIJOHBTQSJOHBOE"DUJWJUZ CA "TLTUVEFOUTUPQSPEVDFBTQJEFSHSBNGPSUIJTUPQJDVTJOHUIFTVNNBSZBTBHVJEF DPVMEXPSLJOBTNBMMHSPVQUPFODPVSBHFEJTDVTTJPOBCPVUUIFTVCKFDUBOEUIF NBLFBDPQZPGUIFGJOBMEJBHSBN Activities t*EFOUJGZFWFSZEBZGPSDFTTVDIBTQVTIQVMMUVSOUXJTUPSTRVFF[F t*EFOUJGZFWFSZEBZFYBNQMFTPGJOFSUJB t1SBDUJTFQMPUUJOHMPBEoFYUFOTJPOHSBQITBOEDBMDVMBUJOHUIFTQSJOHDPOTUBOU Resources http://www.physicsclassroom.com/class/newtlaws/u2l1b.cfm Where next? e next section introduces Newton’s second law of motion and explains the relationship between the applied force, mass and resultant change in motion. Grade 9 39 6OJU'PSDFBOE/FXUPOTMBXTPGNPUJPO Answers to review questions 1. Students should list a number of forces and identify them as contact or noncontact. Most will already have been covered as an activity. 2. Every body remains stationary or moves with uniform motion in a straight line unless acted upon by a force. 3. Hooke’s law states that the force applied to a spring is directly proportional to the extension, provided the elastic limit has not been passed. A spring has undergone elastic deformation if it obeys Hooke’s law and returns to its original length when the force is removed. e elastic limit is the point beyond which force and extension are no longer proportional. A spring has undergone plastic deformation if the elastic limit is passed; it stretches more than expected and will not return to its original length when the force is removed. 4. force stiff spring weak spring extension 5IJTTFDUJPO TIPVME /FXUPOhTTFDPOEMBX GJMMBQQSPYJNBUFMZ 2 periods of Learning Competencies UFBDIJOHUJNF #ZUIFFOEPGUIJTTFDUJPOTUVEFOUTTIPVMECFBCMFUP t %JTUJOHVJTICFUXFFOSFTVMUBOUGPSDFBOEFRVJMJCSBOUGPSDF t %FTDSJCFUIFFGGFDUPGBGPSDFBDUJOHPOBCPEZ t "QQMZ/FXUPOTTFDPOEMBXnet BT=FmaUPTPMWFQSPCMFNT t 3FTPMWFGPSDFTJOUPSFDUBOHVMBSDPNQPOFOUTBOEDPNQPTFGPS BCPEZVTJOHDPNQPOFOUNFUIPET t %FTDSJCFUIFUFSNXFJHIUBOEXFJHIUMFTTOFTTJODMVEJOHEJTUJOHV CFUXFFOXFJHIUBOEBQQBSFOUXFJHIU t $BMDVMBUFUIFXFJHIUBOEBQQBSFOUXFJHIUPGBOPCKFDUJOBSBOHFP TJUVBUJPOT Starting off is section builds on Unit 1, Vectors. Forces are vectors; they can be added and subtracted using the principles from section 1.2. Students need to be able to calculate resultant forces using both scale diagrams and trigonometry. It is 40 Grade 9 6OJU'PSDFBOE/FXUPOTMBXTPGNPUJPO BEWJTBCMFUPTQFOEBUMFBTUPOFMFTTPOSFWJTJUJOHUIFUFDIOJRVFTVTFEGPSTVDI calculations. Two misconceptions are examined – the dierence between mass and weight – as well as the idea of weightlessness. Teaching notes Begin by revisiting the methods used to resolve vectors. Demonstrate what is meant by the resultant of a vector. Use a large rigid box and ask two students to push it on two adjacent sides. It will move at an angle. If one student pushes a lot harder, the angle at which the box moves will change. Another student can then push the box at one point in the direction it moved. is represents the resultant force of the two forces. A fourth student pushes the box from the other side in the opposite direction with the same force. e box EPFTOPUNPWFJTGPVSUITUVEFOUJTQSPWJEJOHUIFFRVJMJCSBOUGPSDF Now ask the rst two students to repeat their pushing and the fourth student to oppose. e box does not move. ere is no resultant (or net) force on the box and we say that the forces are balanced. Students should practice using scale diagrams and trigonometry to calculate the resultant of two forces acting at a variety of angles to one another. When forces are not balanced, Newton’s rst law states that the object should speed up, slow down or change direction. is means the object will accelerate. Use ice cubes on a table to show the eect of a small push on a small ice cube. A big push on the same ice cube produces a bigger acceleration. A small push on a large block of ice produces a very small acceleration. is will lead on to an explanation of Newton’s second law; acceleration is directly proportional to resultant force and takes place in the same direction as the resultant force. When introducing the idea of mass and weight, you could ask students if they know their weight. ose who do will probably answer in kilograms. Weight is a force and is therefore measured in newtons. Mass is a measure of the amount of material in a body and weight is a result of gravitational attraction on the mass. To 'put on weight' without changing your diet, move close to the North or South Pole or visit Jupiter, Saturn or Neptune. To 'lose weight' move even closer to the FRVBUPSPSWJTJUUIF.PPO.FSDVSZ.BSTPS1MVUPFXFJHIUPGBOPCKFDUPOUIF other planets is very similar to its weight on Earth. e concept of being weightless is oen misunderstood. Students will have seen pictures of astronauts oating around in their spacecra. ey appear to be weightless. If they are in orbit around the Earth, they are falling to Earth at the same rate as the spacecra is falling to Earth and the Earth is falling away beneath as the spacecra orbits. ey are still being attracted towards the Earth, therefore they have weight. If they stood on a pair of scales in the spacecra, they would appear to be weightless. Use a spring balance to illustrate 'weightlessness'. Hang a mass on the spring balance. Choose a mass that gives almost a maximum reading. Hold the spring balance at arms length with your arm out straight in front. Lower your arm suddenly. e reading on the balance becomes smaller. e mass has lost weight. Now drop the spring balance onto a foam mat. As it falls, the mass appears to be weightless, but obviously still has weight as it is attracted towards the Earth by gravity. = ma for a variety of situations. 4UVEFOUTTIPVMEQSBDUJDFUIFVTFPGUIF F netFRVBUJPO Grade 9 41 6OJU'PSDFBOE/FXUPOTMBXTPGNPUJPO SA = starter activity MA = main activity CA = concluding activity Forces and acceleration SA "TLTUVEFOUTUPFYQMBJOIPXUPDPNCJOFOPOQBSBMMFMBOEOPOQFSQFOEJDVMBSW MA .PWJOHBCPYBOE/FXUPOTTFDPOEMBXXJUIJDFDVCFTTFFQBHF#PUIPGUIFTFDPVMECF EPOFJOTNBMMHSPVQTJGFRVJQNFOUBMMPXT CA 3FWJFXRVFTUJPOT¦ Acceleration calculations SA "MMPXTUVEFOUTUPAXFJHIWBSJPVTTNBMMPCKFDUT MA CA 8IBUJTUIFEJGGFSFODFCFUXFFOXFJHIUBOENBTT %JTDVTTJOTNBMMHSPVQTBOEGFFE JEFBT%JTDVTTBQQBSFOUXFJHIUMFTTOFTTBOEUSVFXFJHIUMFTTOFTTXJUIBQBSUOFS UPHFUIFSXJUIBOPUIFSQBJSUPQPPMJEFBTCFGPSFGFFEJOHCBDLUPSFTUPGDMBTT 3FWJFXRVFTUJPO Activities t*EFOUJGZGPSDFTBDUJOHJODMVEJOHFRVJMJCSBOUGPSDFJOBWBSJFU situations. = ma to solve problems. t6TFUIFFRVBUJPO netF t%JTDVTTQSPCMFNTPGBQQBSFOUXFJHIUMFTTOFTTJOTQBDF Resources http://www.physicsclassroom.com/class/newtlaws/u2l3a.cfm Where next? e next section looks at friction as a force that opposes motion. Students will again need to nd the resultant force acting on an object. e resultant force on an object will be the applied force minus the frictional force. Answers to review questions 1. Resultant: one force that has the same overall eect as a combination of two or more forces. &RVJMJCSBOUGPSDFFRVBMJONBHOJUVEFUPSFTVMUBOUCVUBDUJOH direction. 2. e acceleration produced when a resultant force acts on an object is directly proportional to the resultant force and acts in the same direction as the force. 3. 2.5 m/s2 600 N 40 kg 2N 0.05 m/s2 42 Grade 9 6OJU'PSDFBOE/FXUPOTMBXTPGNPUJPO B/UPMF[FSP/UPSJHIU b) unbalanced; balanced; unbalanced c) 1 m/s2UPMF[FSPNT 2 to right 5. Mass: measure of the amount of material in an object measured in kilograms. Weight: measure of the gravitational attraction on an object measured in newtons. 'SJDUJPOBMGPSDF Learning Competencies 5IJTTFDUJPO TIPVME GJMMBQQSPYJNBUFMZ 3 periods of UFBDIJOHUJNF #ZUIFFOEPGUIJTTFDUJPOTUVEFOUTTIPVMECFBCMFUP t &YQMBJOUIFDBVTFTPGGSJDUJPOBMGPSDFT t %FTDSJCFUIFEJGGFSFODFTCFUXFFOMJNJUJOHGSJDUJPOTUBUJDGSJDUJPOBOE LJOFUJDGSJDUJPO t %SBXGSFFCPEZEJBHSBNTGPSPCKFDUTPOJODMJOFEQMBOFTUPJODMVEF GSJDUJPOBMGPSDFTBOEVTFUIFTFEJBHSBNTUPTPMWFQSPCMFNT Starting off is section introduces the concept of friction as a force that opposes motion. 8FGSFRVFOUMZOFFEUPSFEVDFGSJDUJPOCVUUIFSFBSFOVNFSPVTPDDBTJPOTXIFSF friction is useful and we could not do without it. ere are opportunities for students to perform their own experiments using newtonmeters as they investigate friction. Teaching notes Begin by asking the students whether they think friction is a good or bad thing. Most will say that it is a nuisance that needs to be overcome. ey will know that cars need oil in the engine and bicycles need oil on the wheel bearings to reduce friction. If friction is not reduced, the friction causes heating and can lead to the DBSFOHJOFTFJ[JOHVQPSUIFCJDZDMFXIFFMTCFDPNJOHWFSZEJDVMUUPUVSO Ask them to imagine riding a bicycle or driving a car if there is no friction between the tyres and the road surface. e wheels would spin and the vehicle would not move. e car parking brake locks the car’s wheels and stops the car moving if it is parked on an incline; but if there was no friction between the tyres and the road, the car would slide downhill. Even the simple act of walking to school uses friction between the soles of the shoes and the road. Striking a match uses the principle that friction, between the match head and the box, produces enough heat to ignite the chemical in the match head. Even the smoothest surface has small bumps that stop the surface sliding overActivity 3.4: Answer another. Sandpaper is a very rough surface where these bumps are visible, 4UVEFOUThPXO but when looked at under a powerful microscope, even glass has bumps like results sandpaper on its surface. Grade 9 43 6OJU'PSDFBOE/FXUPOTMBXTPGNPUJPO ere are two types of frictional force. Static friction is the force that is acting until an object starts to move; kinetic friction acts while the object is actually moving. Static friction increases as the force trying to start an object moving increases. Eventually, the applied force is greater than the static friction and the object moves. e maximum value of static friction is known as the limiting friction. Students should use newtonmeters to pull a relatively heavy object across a surface. It is important that they increase the force gradually. ey should notice the reading on the newtonmeter increases to a maximum and then drops down again. e force needed to keep the object moving, and overcome kinetic friction, is less than the limiting friction. Competitors in the World’s Strongest Man oen have to pull heavy loads. ey have pulled lorries, train engines, even aircra. Once they have overcome limiting friction, the reduction in frictional force to that of kinetic friction oen means that the pull rope becomes slack. 8IFOQVMMJOHBOPCKFDUPWFSBIPSJ[POUBMTVSGBDFTUVEFOUTDBODBM coecient of friction. e normal contact force will in this case be the weight. ey can compare the coecients of friction for a number of pairs of surfaces and the eect of polishing one surface or adding a lubricant between the surfaces. e coecient of friction depends on the two surfaces; it does not apply to a particular material. When an object is on an inclined plane, the normal contact force is less. e weight acts vertically downwards but the normal contact force acts at right angles UPUIFTVSGBDFBOEJTFRVBMUPw cos , where is the angle of the incline to the IPSJ[POUBM4UVEFOUTDBOVTFOFXUPONFUFSTUPJOWFTUJHBUFGSJDUJP inclined planes. SA = starter activity MA = main activity CA = concluding activity Causes and types of friction SA *OTNBMMHSPVQTEJTDVTTAJTGSJDUJPOBHPPEPSBCBEUIJOH 'FFECBDLJEFBT MA *OWFTUJHBUFGPSDFOFFEFEUPQVMMCPYPWFSWBSJPVTTVSGBDFT CA %JTDVTTSFTVMUTPGJOWFTUJHBUJPOUPVTFOFYUMFTTPO Factors affecting frictional force SA 3FWJFXSFTVMUTPGJOWFTUJHBUJPOGSPNMBTUMFTTPOBOEBTLTUVEFOUTUPBUUFNQ MA "DUJWJUZBOEFYQMPSFGSJDUJPOBOEJODMJOFEQMBOFT CA 'VSUIFSFYBNQMFTPGDBMDVMBUJOHGSJDUJPOGPSDFUPCFUBDLMFEJOQBJST Reducing friction and the effects of friction SA %JTDVTTXBZTPGSFEVDJOHGSJDUJPOJOTNBMMHSPVQT MA 3FQFBUBDUJWJUZCVUUIJTUJNFBEEMVCSJDBOUTCFUXFFOTVSGBDFBOECMPDLoDPN XJUIQSFWJPVTMFTTPO CA %JTDVTTBEWBOUBHFTBOEEJTBEWBOUBHFTPGGSJDUJPOJOTNBMMHSPVQT1SPEVDF 3FWJFXRVFTUJPOT¦ 44 Grade 9 6OJU'PSDFBOE/FXUPOTMBXTPGNPUJPO Activities t6TFBOFXUPONFUFSUPNFBTVSFTUBUJDGSJDUJPOMJNJUJOHGSJDUJPOBOELJOFUJD friction. t6TFUIFFRVBUJPOF = N to measure coecient of friction between various surfaces. t6TFBOFXUPONFUFSUPFYBNJOFUIFFFDUPGQPMJTIJOHBTVSGBDFPSVTJOHB lubricant between two surfaces. Resources http://www.mathsrevision.net/alevel/pages.php?page = 79 Where next? e next section looks at what happens when a force is applied. Forces always come in pairs. Whenever a force is applied to an object, the object applies a force in return. Answers to review questions 1. Friction is caused by tiny bumps in the surfaces of objects rubbing together as one surface moves over the other. e roughness of the surface is the most important factor aecting friction. 2. Static friction: frictional force between two surfaces that are trying to move past each other but are not yet moving Kinetic friction : frictional force between two surfaces that are moving past each other 3. 1.24 N 4. Useful: lighting match; tyres gripping road; brakes Disadvantage: bearings; hinge; sawing; car engine /FXUPOTUIJSEMBX Learning Competencies 5IJTTFDUJPO TIPVME GJMMBQQSPYJNBUFMZ 4 periods of UFBDIJOHUJNF #ZUIFFOEPGUIJTTFDUJPOTUVEFOUTTIPVMECFBCMFUP t 4UBUF/FXUPOTUIJSEMBX t %FTDSJCFFYQFSJNFOUTUPEFNPOTUSBUFJUBOEHJWFFYBNQMFTPGXIFSFJUJT BQQMJDBCMF Starting off is section introduces the idea of force pairs. Forces do not act in isolation. If you push an object with a force F, it will push you with the same force F in the opposite direction. Grade 9 45 6OJU'PSDFBOE/FXUPOTMBXTPGNPUJPO Teaching notes Begin by showing the students what happens when you nose cone release a fully inated balloon that has not been tied o. It moves through the air. pressurised air A more dramatic demonstration is to use a water rocket.pop bottle A simple rocket can be built using an empty plastic water CPUUMF)BMGMMXJUIXBUFSBOENBLFBOP[[MFGSPNB rubber bung and a length of tubing passing into the bottle fins through a hole in the bung. Use a bicycle pump or a foot nozzle pump to pump air into the bottle. When the pressure is expelled water high enough, the bung will be forced out; the pressurised air expels the water, which in turn creates the thrust to accelerate the rocket. Some water rockets have reached speeds of up to 200 km/h and heights of 300 m! FSFJTBGPSDFQVTIJOHUIFXBUFSPVUPGUIFCPUUMFBOFRVBMBOEPQQPTJ pushes the bottle up into the air. Activity 3.5: Answer Both students NPWF is is the principle behind rockets that blast astronauts into space, the jet engine, the hovercra. Ask students to explain how their bicycle wheels use force pairs. In which direction does the wheel push? In which direction does the bicycle move? SA = starter activity MA = main activity CA = concluding activity The third law SA "TLTUVEFOUTUPRVPUFGJSTUBOETFDPOEMBXTJOUIFJSPXOXPSETBOEFYQMBJONFBO MA %FNPOTUSBUJPOTEFTDSJCFEPOQBHFBOEBTLTUVEFOUTUPSFTFBSDIVTFPGUIJTMBXJ KFUFOHJOFTBOEIPWFSDSBGU CA 'FFECBDLGSPNSFTFBSDI Newton’s pair forces SA %JTDVTTIPXCJDZDMFXIFFMTVTFGPSDFQBJST MA &YQMPSFGPSDFQBJSTJOUIFDMBTTSPPNBOEBSPVOEUIFTDIPPM-JTUBTNBOZBTQPTTJ CA 'FFECBDLGSPNBDUJWJUZ Applications of the third law (1) SA "TLTUVEFOUTUPXPSLJOTNBMMHSPVQTUPEJTDVTTGPSDFTNJTTJOHJO'JHVSFPOQBHF 4UVEFOUTh#PPL MA 4UVEFOUTXPSLJOQBJSTUPUBDLMFFYBNQMFTPGVTFPGUIJSEMBX CA %JTDVTTBOTXFSTUPBDUJWJUZ Applications of the third law (2) SA -JTUBQQMJDBUJPOTPGUIFUIJSEMBXXJUIBQBSUOFS%JTDVTTJEFBTXJUIBOPUIFSQBJS MA "DUJWJUZ CA 3FWJFXRVFTUJPOT¦ 46 Grade 9 6OJU'PSDFBOE/FXUPOTMBXTPGNPUJPO Activities t%FTDSJCFBOEFYQMBJOXIBUIBQQFOTUPBTUVEFOUPOSPMMFSTLBUFTXIPUSJFTUP push over a wall. t4UVEFOUTTIPVMEXPSLJOQBJSTTUBOEJOHPOTLBUFCPBSETPSSPMMFSTLBUFTBOE holding a rope between them. What happens when one of them gives a sharp tug on the rope? Resources http://www.grc.nasa.gov/WWW/k-12/airplane/newton3.html http://exploration.grc.nasa.gov/education/rocket/newton3r.html http://inventorsabout.com/library/inventors/blrockerprinciples.htm http://scs8wikinotes.wetpaint.com/Ryan+McCaig+Hovercra http://www.physicsclassroom.com/class/newtlaws/U214a.cfm Where next? e next section introduces the concept of momentum and revisits Newton’s second law of motion by stating it in terms of momentum instead of mass and acceleration. Answers to review questions 5PFWFSZBDUJPOUIFSFJTBOFRVBMBOEPQQPTJUFSFBDUJPO FRVBMJONBHOJUVEF opposite in direction act on dierent objects be the same type of force any three examples that identify the two forces acting correctly $POTFSWBUJPOPGMJOFBSNPNFOUVN Learning Competencies 5IJTTFDUJPO TIPVME GJMMBQQSPYJNBUFMZ 3 periods of UFBDIJOHUJNF #ZUIFFOEPGUIJTTFDUJPOTUVEFOUTTIPVMECFBCMFUP t %FGJOFMJOFBSNPNFOUVNBOETUBUFJUTVOJUT t 4UBUFUIFMBXPGDPOTFSWBUJPOPGNPNFOUVN t %FGJOFUIFUFSNJNQVMTFBOETUBUFJUTVOJUT t 4PMWFOVNFSJDBMQSPCMFNTSFMBUJOHUPNPNFOUVNDPOTFSWBUJPOPG NPNFOUVNBOEJNQVMTF t 4UBUF/FXUPOTTFDPOEMBXJOUFSNTPGNPNFOUVN Grade 9 47 6OJU'PSDFBOE/FXUPOTMBXTPGNPUJPO Starting off is section builds on the idea of inertia as the reluctance of a body to start or stop moving. Momentum is a measure of how hard it is to stop a moving body and depends on both its mass and velocity. Teaching notes Begin by asking the students to imagine trying to stop an animal running towards them. Which is harder to stop, an elephant or a mouse both moving at the same speed? en imagine trying to tackle a rugby player walking with the ball towards the touch line and then trying to tackle the same player running with the ball. e elephant has a greater mass than the mouse and the running rugby player has a greater velocity than when he is walking. It is harder to stop the elephant and the running rugby player, because they have the greater momentum. Trains have a large mass and a high velocity. A 1000 tonne train travelling at 150 km/h will need a distance of at least 1 km to stop with the most advanced braking system available. Remind students that mass is a scalar and velocity a vector. When a scalar is multiplied by a vector, the result is a vector. is means that momentum is a vector. Ask students what they understand by the word conservation. ey may answer in terms of endangered species being protected. In physics, conservation relates UPUIFUPUBMRVBOUJUJFTXJUIJOBTZTUFNCFJOHVODIBOHFEBUUIFFOEPG process, provided there is no external inuence. Conservation of momentum applies whenever there is a collision or an explosion. Ask the students to think about a rugby player being tackled. If two players of FRVBMNBTTBSFSVOOJOHUPXBSETPOFBOPUIFSBUUIFTBNFWFMPDJUZUIF the same magnitude of momentum but in opposite directions. e two players BSFUIFDMPTFETZTUFN#FDBVTFUIFNPNFOUVNTBSFFRVBMBOEPQQPTJUFU DPNCJOFENPNFOUVNCFGPSFUIFDPMMJTJPOJT[FSP#FDBVTFNPNFOUVNJO system is conserved aer the collision, the combined momentum aer collision is [FSP"TUIJTJTUIFQSPEVDUPGUIFJSDPNCJOFENBTTBOEWFMPDJUZUIFOBMW NVTUCF[FSPBTUIFJSDPNCJOFENBTTDBOOPUCF[FSPF[FSPOBMWFMPDJUZ be achieved in two ways. Either they both remain stationary or they rebound away from one another with the same magnitude of velocity. Ask the students to describe what could happen if the player with the ball has a greater mass; the player with the ball is running faster; the player tackling has a greater mass; the player tackling is running faster. Demonstrate what happens during collisions by using toy cars with wheels that turn freely. e mass of these can be changed by adding Plasticine and they can be made to join together if small magnets are attached. Explosions are more dicult to demonstrate, but students can think about what happens to a gun when a bullet is red or a rocket when exhaust gases are ejected at high speed. As a demonstration, use a container, such as a 35 mm lm canister, XJUIBGBJSMZUJHIUUUJOHMJE"EEBTNBMMRVBOUJUZPGTPEJVNCJDBSCPO WJOFHBSJOUIFDBOJTUFSBOERVJDLMZQVTIPOUIFMJE1MBDFUIFDBOJTUF and make sure there is a safety screen to protect the students. e gas produced will cause the cap to be blown o with a relatively high velocity, but the canister will also move backwards with a smaller velocity. 48 Grade 9 6OJU'PSDFBOE/FXUPOTMBXTPGNPUJPO *OTFDUJPOTUVEFOUTMFBSOFEUIFFRVBUJPO as a Fform = ma of Newton’s second Activity 3.6: Answer law of motion. is is true for a constant mass. Acceleration is the change in NBTTFT o CPUI velocity divided by time and can be written as v/t. Force is therefore written &RVBM TUVEFOUTNPWF as F = m v/t. Mass can be included within the rate of change so F = /t, mv XIJDIJTBOPUIFSXBZPGTUBUJOH/FXUPOTTFDPOEMBXUIBUGPSDFJTFRVBM UPUIFSBUF %JGGFSFOU NBTTFTo of change of momentum. SFTVMUTEFQFOEPO Ask students to think about why a footballer follows through with his foot and aSBUJPPGNBTTFT golfer follows through with the golf club aer striking the ball. is will introduce the idea of impulse. Explain the worked example in the Students' Book. SA = starter activity MA = main activity CA = concluding activity What is linear momentum? SA 4UVEFOUTXPSLJOTNBMMHSPVQTUPEJTDVTTUIFRVFTUJPOA8IJDIJTIBSEFSUPTUPQB PSBNPVTFJGUIFZBSFCPUINPWJOHBUUIFTBNFTQFFE 8IZ MA 4UVEFOUTXPSLJOQBJSTUPUBDLMFFYBNQMFTPGVTFPGNPNFOUVNDBMDVMBUJPOT CA *OTNBMMHSPVQTMJTUFYBNQMFTPGNPNFOUVNJOFWFSZEBZMJGF The law of conservation of linear momentum SA "TLTUVEFOUTXIBUUIFZVOEFSTUBOECZADPOTFSWBUJPO&YQMBJOXIBUJUNFBOTJOQ MA "DUJWJUZBOEEFNPOTUSBUJPOTTFFQBHFPGUIJTCPPL CA 3FWJFXRVFTUJPOT¦ Momentum and Newton’s laws SA "TLTUVEFOUTUPHJWF/FXUPOTTFDPOEMBXJOUIFJSPXOXPSET*OTNBMMHSPVQTUIFZ IPXJUJTSFMBUFEUPNPNFOUVN MA 4UVEFOUTEJTDVTTFYBNQMFTPGJNQVMTFGSPNFWFSZEBZMJGF3FWJFXRVFTUJPOT CA *OTNBMMHSPVQTTUVEFOUTEJTDVTTAXIZEPFTBGPPUCBMMFSGPMMPXUISPVHIXJUII TUSJLJOHUIFCBMM BOEAXIZEPFTBHPMGFSGPMMPXUISPVHIXJUIUIFDMVCBGUFSTUS CBMM Activities t*EFOUJGZFWFSZEBZFYBNQMFTPGNPNFOUVNDPOTFSWBUJPO t6TFUIFQSJODJQMFPGDPOTFSWBUJPOPGNPNFOUVNUPDBMDVMBUFXIBUIBQQFOT during collisions and explosions. t6TFUIFQSJODJQMFPGDPOTFSWBUJPOPGNPNFOUVNUPFYQMBJOXIZUIF acceleration of a rocket increases as it leaves the launch pad when there is a constant thrust. Resources http://www.antoine-education.co.uk/Physics_AS/Module_2/Topic_7/topic_7_ momentum.htm http://www.fearofphysics.com/probs/conservation_of_momentum.html XXXRVJBDPNKRIUNM XXXRVJBDPNNDIUNM Grade 9 49 6OJU'PSDFBOE/FXUPOTMBXTPGNPUJPO Where next? e next section looks at the dierence between elastic and inelastic collisions. e conservation of energy is introduced. Answers to review questions 1. Linear momentum is dened as the product of mass and velocity and is measured in kg m/s 2. 36 000 kg m/s 3. 500 × 24 = (500 + 100) × 20 4. 16 m/s 5. momentum change = (6 × 4) – (– (6 × 4)) 5IJTTFDUJPO TIPVME $PMMJTJPOT GJMMBQQSPYJNBUFMZ 2 periods of Learning Competencies UFBDIJOHUJNF #ZUIFFOEPGUIJTTFDUJPOTUVEFOUTTIPVMECFBCMFUP t %JTUJOHVJTICFUXFFOFMBTUJDBOEJOFMBTUJDDPMMJTJPOT Starting off is section builds on the study of conservation of momentum by examining dierent types of collision. e concept of conservation of kinetic energy is introduced. Teaching notes Show the dierence between elastic and inelastic collisions by a steel ball, a rubber ball and a ball of playdough onto a solid steel surface. Provided the height is not too great, the steel ball will rebound higher than the rubber ball. e playdough ball will probably not rebound at all. Steel is almost perfectly elastic and playdough almost perfectly inelastic. In a perfectly elastic collision, the velocity aer collision is the same as the velocity before collision. is means that kinetic energy is conserved as well as momentum. *OBQFSGFDUMZJOFMBTUJDDPMMJTJPOUIFWFMPDJUZBFSDPMMJTJPOJT[ is not conserved. When a tennis ball is dropped onto grass, it bounces. When the same ball is dropped from the same height onto articial turf, the velocity of its rebound is almost double that of when it bounces on grass. 50 Grade 9 6OJU'PSDFBOE/FXUPOTMBXTPGNPUJPO SA = starter activity MA = main activity CA = concluding activity Elastic collisions SA 4UVEFOUTXPSLJOTNBMMHSPVQTUPEJTDVTTUIFRVFTUJPOAXIBUIBQQFOTXIFOBTOP IJUTBOPUIFSCBMMPSUIFTJEFPGUIFUBCMF MA 4UVEFOUTXPSLJOTNBMMHSPVQTUPFYQMPSFFMBTUJDDPMMJTJPOTXJUITUFFMCBM CA *OTNBMMHSPVQEJTDVTTXIBUJTDPOTFSWFEJODPMMJTJPOTBOEXIBUNBZDIBOHF Inelastic collisions SA *OTNBMMHSPVQTTUVEFOUTESPQBUFOOJTCBMMPOBEFTLBOEPCTFSWFXIBUIBQQFO DPOTFSWFE 8IBUJTSFEVDFE MA &YQMPSFESPQQJOHBUFOOJTCBMMGSPNUIFTBNFIFJHIUPOUPWBSJPVTTVSGBDFT3F CPVODFCBDL CA 3FWJFXRVFTUJPO*OTNBMMHSPVQTEJTDVTTXIZTPNFUFOOJTQMBZFSTQSFGFSUPQM BOEPUIFSTQSFGFSBOBSUJGJDJBMTVSGBDF Activities t1SPWJEFFYBNQMFTPGDPMMJTJPOTUIBUBSFBMNPTUQFSGFDUMZFMBTUJDBOEBMNPTU perfectly inelastic. t%JTDVTTSFBTPOTXIZTPNFUFOOJTQMBZFSTQSFGFSUPQMBZUFOOJTPOBOBSUJDJBM grass court and why some prefer to play on grass. Where next? e next section returns to Newton’s rst law of motion and combining vectors to OEPVUXIFUIFSPSOPUBTZTUFNPGGPSDFTJTJOFRVJMJCSJVN Answers to review questions 1. In elastic collisions, kinetic energy is conserved and the velocity aer collision JTOVNFSJDBMMZFRVBMUPUIFWFMPDJUZQSJPSUPDPMMJTJPO 5IFGJSTUDPOEJUJPOPGFRVJMJCSJVN Learning Competencies 5IJTTFDUJPO TIPVME GJMMBQQSPYJNBUFMZ 3 periods of UFBDIJOHUJNF #ZUIFFOEPGUIJTTFDUJPOTUVEFOUTTIPVMECFBCMFUP t 4UBUFUIFDPOEJUJPOTSFRVJSFEGPSMJOFBSFRVJMJCSJVN t %FDJEFXIFUIFSBTZTUFNJTJOFRVJMJCSJVN t "QQMZUIFGJSTUDPOEJUJPOPGFRVJMJCSJVNUPTPMWFQSPCMFNT Starting off is section builds on Unit 1 and Newton’s rst law of motion. A body is in linear FRVJMJCSJVNJGUIFTVNPGBMMPGUIFGPSDFTBDUJOHPOUIFCPEZJT[FSP Grade 9 51 6OJU'PSDFBOE/FXUPOTMBXTPGNPUJPO Teaching notes FFBTJFTUXBZGPSTUVEFOUTUPVOEFSTUBOEUIFDPODFQUPGFRVJMJCSJV the use of free body diagrams. Start by asking three students to use newtonmeters to pull on a block of wood. e wood should have a number of hooks on it so that newtonmeters can be attached at various points. ey should pull in various directions to keep the block TUBUJPOBSZJOUIFBJS8IFOUIFCMPDLJTJOFRVJMJCSJVNSFDPSEUIFNBHOJ direction of each force. Repeat the investigation by changing the directions and magnitude of the forces, then increase to use four, ve or six newtonmeters. SA = starter activity MA = main activity CA = concluding activity The conditions of equilibrium SA 4UVEFOUTEJTDVTTXIBUUIFZVOEFSTUBOECZAFRVJMJCSJVNXJUIBQBSUOFSBOEUIFOG JEFBT MA *OWFTUJHBUFQVMMJOHPOBCMPDLPGXPPEXJUIOFXUPONFUFST CA 8PSLXJUIBQBSUOFSUPESBXGSFFCPEZEJBHSBNTGPSUIFSFTVMUTPGUIFJOWFTUJHBU Is a system in equilibrium? SA 8JUIBQBSUOFSVTFUIFGSFFCPEZEJBHSBNTGSPNMBTUMFTTPOUPTIPXUIBUUIFCPEZXB FRVJMJCSJVN MA 4UVEFOUTXPSLXJUIBQBSUOFSUPMJTUFYBNQMFTPGTZTUFNTJOFRVJMJCSJVNUIFZNF FWFSZEBZMJGF CA 3FWJFXRVFTUJPOT¦ Applying the first condition of equilibrium SA "TLTUVEFOUTUPFYQMBJOUIFGJSTUDPOEJUJPOPGFRVJMJCSJVNUPBQBSUOFSBOEUIF JEFBT MA 4UVEFOUTUBDLMFQSPCMFNTJOWPMWJOHUIFGJSTUDPOEJUJPOPGFRVJMJCSJVNXJU CA &OEPGVOJURVFTUJPOT Activities t6TFUIFEBUBGSPNUIFJOWFTUJHBUJPOUPESBXGSFFCPEZEJBHSBNTUPQ CMPDLXBTJOMJOFBSFRVJMJCSJVN Resources http://www.physicsforums.com/showthread.php?t = 283326 http://www.uxl.eiu.edu/~cfadd/1150/08statics/rst.html Where next? e next unit examines what happens when forces do work. Work is done when a force is moved through a distance. When work is done, energy is used and the rate at which energy is used (or work is done) determines the power. Collisions are dealt with in more detail as the eect of conservation of kinetic energy is considered. 52 Grade 9 6OJU'PSDFBOE/FXUPOTMBXTPGNPUJPO Answers to review questions "OPCKFDUJTJOMJOFBSFRVJMJCSJVNJGUIFSFJTOPSFTVMUBOUGPSDFBDUJOHPOJU 2. 51 N; angle of 11.3° to 50 N force. Answers to end of unit questions 1.Every body remains stationary or moves with uniform motion in a straight line unless acted upon by a force. Acceleration is proportional to the applied force and takes place in the same direction as the force. OR e resultant force acting on a body is proportional to the rate of change of linear momentum of the body. 5PFWFSZBDUJPOUIFSFJTBOFRVBMBOEPQQPTJUFSFBDUJPO 2. Inertia is the reluctance of a body to start moving when stationary and stop moving if moving; the greater its mass, the more inertia it has. 3. a) 500 N/m b) 50 mm, provided the elastic limit is not exceeded c) 2.5 N 4. a) 120 N b) 5 N c) 0.2 N d) 45.6 N; 1.9 N; 0.076 N 5. 120 N 6. 3.16 m/s2; 18.4° to 6000 N force 7. 0.82 m/s2 8. In a closed system, the total linear momentum remains constant. If no external forces are acting, the momentum before a collision/explosion is the same as it is aer the collision/explosion. 9. a) 5 kg m/s b) 5 kg m/s c) 500 m/s 10.160 N; 1600 N Grade 9 53 Work, energy and power Unit 4 Learning Competencies for Unit 4 This unit should GJMMBQQSPYJNBUFMZ By the end of this unit students should be able to: 11 periods of t %FTDSJCFUIFOFDFTTBSZDPOEJUJPOTGPSXPSLUPCFEPOFCZBGPSDF UFBDIJOHUJNF JODMVEJOHXPSLEPOFCZBGPSDFFBDUJOHPOBCPEZBUBOBOHMFPG t the horizontal). t 6TFW = F s cos to solve problems. t $BMDVMBUFUIFXPSLEPOFBHBJOTUHSBWJUZUIFXPSLEPOFCZBGSJDUJ BOEUIFXPSLEPOFCZBWBSJBCMFGPSDF t %JTUJOHVJTICFUXFFOOFHBUJWFBOEQPTJUJWFXPSL t &YQMBJOUIFSFMBUJPOTIJQCFUXFFOXPSLBOEFOFSHZ t %FSJWFUIFSFMBUJPOTIJQCFUXFFOXPSLBOELJOFUJDFOFSHZBOEVTFU solve problems. t 4IPXUIFSFMBUJPOTIJQCFUXFFOXPSLBOEQPUFOUJBMFOFSHZBTW = U use this to solve problems. t %FTDSJCFHSBWJUBUJPOBMQPUFOUJBMFOFSHZBOEFMBTUJDQPUFOU t &YQMBJONFDIBOJDBMFOFSHZBTUIFTVNPGLJOFUJDBOEQPUFOUJBMFO t 4UBUFUIFMBXPGDPOTFSWBUJPOPGNFDIBOJDBMFOFSHZ t 3FWJTFUIFUFSNDPMMJTJPOBOEEJTUJOHVJTICFUXFFOFMBTUJDBOEJO DPMMJTJPOT t 4PMWFQSPCMFNTJOWPMWJOHJOFMBTUJDDPMMJTJPOTJOPOFEJNFOT MBXTPGDPOTFSWBUJPOPGNFDIBOJDBMFOFSHZBOENPNFOUVN t &YQMBJOUIFFOFSHZDIBOHFTUIBUUBLFQMBDFJOBOPTDJMMBUJOHQFO BOEBOPTDJMMBUJOHTQSJOHoNBTTTZTUFN t %FTDSJCFUIFVTFPGFOFSHZSFTPVSDFTJODMVEJOHXJOEFOFSHZTPMB BOEHFPUIFSNBMFOFSHZ t &YQMBJOUIFNFBOJOHPGUIFUFSNSFOFXBCMFFOFSHZ t 4PMWFQSPCMFNTSFMBUJOHUPUIFEFGJOJUJPOPGQPXFS t 4IPXUIBUUIFL8IJTBMTPBVOJUPGXPSL t &YQSFTTUIFGPSNVMBPGNFDIBOJDBMQPXFSJOUFSNTPGBWFSBHFWFM 54 Grade 9 6OJU8PSLFOFSHZBOEQPXFS .FDIBOJDBMXPSL Learning Competencies 5IJTTFDUJPO TIPVME GJMMBQQSPYJNBUFMZ 2 periods of UFBDIJOHUJNF #ZUIFFOEPGUIJTTFDUJPOTUVEFOUTTIPVMECFBCMFUP t %FTDSJCFUIFOFDFTTBSZDPOEJUJPOTGPSXPSLUPCFEPOFCZBGPSDF JODMVEJOHXPSLEPOFCZBGPSDFFBDUJOHPOBCPEZBUBOBOHMFPG to the horizontal). t 6TFW = F s cos to solve problems. t $BMDVMBUFUIFXPSLEPOFBHBJOTUHSBWJUZUIFXPSLEPOFCZBGSJDUJPOGPSDF BOEUIFXPSLEPOFCZBWBSJBCMFGPSDF t %JTUJOHVJTICFUXFFOOFHBUJWFBOEQPTJUJWFXPSL Starting off is topic examines what happens when forces move objects. Work is done and energy is used. Students will probably think that sitting at their desks listening to the teacher or writing in their exercise books is working. Ask them to suggest some examples of work and lead them to the fact that physical work means moving something. Teaching notes It is worth spending a short time discussing the two forms of mechanical energy – kinetic and gravitational potential. Set up a series of experiments for students to look at and decide what is happening to the kinetic and gravitational potential energies when things move. e experiments could include: t BTQSJOHPTDJMMBUPS t BCPYCFJOHQVTIFEBDSPTTUIFPPS t BSVCCFSCBOENPVOUFEWFSUJDBMMZXJUIBNBTTIBOHJOHPOJU t BMPOHTXJOHJOHQFOEVMVN t BNVMUJQMFQVMMFZTZTUFN t BCPVODJOHCBMM Students need to indicate when kinetic energy and gravitational potential energy are increasing, decreasing or staying the same. ey need to decide when each is a minimum and maximum. ey can then start to think about what is doing work and whether the work is being done by or against gravity, against friction, by or against the person performing the experiment and by the object under investigation. When calculating work done, it is not simply a matter of multiplying the weight by the distance moved. When a load is lied vertically, this is the case because work is being done against gravity. When a load is moved horizontally across a surface, no work is done against gravity, only against friction. Students need to be careful not to multiply the weight by the distance moved in this case. If a load is moved up a slope, work is done against gravity and against friction. Students can try moving a 5 kg mass a distance of 1 m vertically, along the table and up a slope. ey will be able to measure the work done by using a newtonmeter to measure the force needed each time. Grade 9 55 6OJU8PSLFOFSHZBOEQPXFS ere is evidence of ramps around the Egyptian pyramids, indicating how the heavy blocks of stone were put in place. Use a simple constant force graph to show that the area under a force–distance graph is equal to the work done. Introduce the idea of varied force and show how the area under an irregular shaped graph can be determined by counting the squares on the graph paper. e idea of negative work is not an easy one to understand. Work is a scalar not a vector so has no direction associated with it. However, there is oen a change in direction of motion associated with negative work. Ask a student to li a 5 kg mass into the air. e gravitational potential energy of the mass has increased. Work has been done theon mass bythe student. e work done is positive. When the student lowers the mass, its gravitational potential energy decreases. Work is donethe by mass onthe student. e work done is negative. Work done is positive if there is a gain in energy and negative if there is a reduction in energy. SA = starter activity MA = main activity CA = concluding activity Work, kinetic and gravitational energy SA 4UVEFOUTXPSLJOHSPVQTUPEJTDVTTBEFGJOJUJPOPGAXPSL'FFECBDLJEFBT-FBEUIFN EFGJOJUJPOVTFEJOQIZTJDTUIBUQIZTJDBMXPSLNFBOTNPWJOHTPNFUIJOH MA 8PSLJOHJOTBNFTNBMMHSPVQTTUVEFOUTFYQMPSFXIBUIBQQFOTUPLJOFUJDBOEHSB FOFSHZJOEJGGFSFOUQIZTJDBMTJUVBUJPOTTFFQBHF CA %JTDVTTXIBUJTEPJOHXPSLJOFBDITJUVBUJPOFYQMPSFEJOUIFNBJOBDUJWJUZBOEXI CFJOHEPOFCZPSBHBJOTUHSBWJUZFUDTFFQBHF Calculating work SA *OTNBMMHSPVQTTUVEFOUTNFBTVSFUIFGPSDFOFFEFEUPNPWFBLHNBTTBEJTUBODFN WFSUJDBMMZCPUIBMPOHBUBCMFBOEVQBTMPQF8IZJTUIFGPSDFSFRVJSFEEJGGFSFO MA *OTBNFTNBMMHSPVQTTUVEFOUTUPNBLFUIFJSPXOTVNNBSZPG4UVEFOUTh#PPLQBHF "TTJTUBTOFDFTTBSZ2VFTUJPOTUVEFOUTUPDIFDLVOEFSTUBOEJOH CA %JTDVTTSFWJFXRVFTUJPOT¦BTBDMBTT4UVEFOUTUPFYQMBJOTUFQTJOUBDLMJOHOV problems. Activities t1SBDUJTFDBMDVMBUJPOTPGXPSLEPOFXIFONPWJOHBCPEZWFSUJDBM or up a slope. t1SBDUJTFDBMDVMBUJOHXPSLEPOFGSPNGPSDFoEJTUBODFHSBQIT Resources www.zonelandeducation.com/mstm/physics/mechanics/energy/work/work.html Where next? Whenever work is done, energy is used. e next unit examines the link between work and energy. 56 Grade 9 6OJU8PSLFOFSHZBOEQPXFS Answers to review questions 1. Work is done when a force moves a body through a distance; any example that involves a force moving an object. 2. a) 400 J b) 2700 J c) 21 000 J d) 20 392 J 1MPUBGPSDFoEJTUBODFHSBQIDPVOUOVNCFSPGTRVBSFTVOEFSHSBQINVMUJQMZ number of squares by area of one square. 1PTJUJWFXPSLJTEPOFJGUIFPCKFDUHBJOTFOFSHZ OFHBUJWFXPSLJTEPOFJGUIF object loses energy. 8PSLoFOFSHZUIFPSFN Learning Competencies #ZUIFFOEPGUIJTTFDUJPOTUVEFOUTTIPVMECFBCMFUP 5IJTTFDUJPO TIPVME GJMMBQQSPYJNBUFMZ t %FSJWFUIFSFMBUJPOTIJQCFUXFFOXPSLBOELJOFUJDFOFSHZBOEVTFUIJTUP 2 periods of solve problems. UFBDIJOHUJNF t 4IPXUIFSFMBUJPOTIJQCFUXFFOXPSLBOEQPUFOUJBMFOFSHZBTW = U and use this to solve problems. t &YQMBJOUIFSFMBUJPOTIJQCFUXFFOXPSLBOEFOFSHZ t %FTDSJCFHSBWJUBUJPOBMQPUFOUJBMFOFSHZBOEFMBTUJDQPUFOUJBMFOFSHZ t &YQMBJONFDIBOJDBMFOFSHZBTUIFTVNPGLJOFUJDBOEQPUFOUJBMFOFSHZ Starting off is section builds on the idea that the more energy a body has the more work it is able to do. Kinetic energy, gravitational potential energy and elastic strain energy are discussed in detail. Teaching notes Activity 4.1: Answer Students will have little concept of what a joule is. ey will know that when a 1 N NPWJOHWFIJDMFT weight is lied 1 m then 1 J of work has been done. To do that work, the personfire liing the weight needs energy. e human body needs energy just to keep itself NVTJD alive and to move itself around. We obtain our energy from food. ere are manyTVOMJHIU websites that provide information about the energy value in various foods, but TV the PG numbers quoted are all in kilojoules. An interesting starter for the students is toTPNFUIJOHBUUPQ stairs have a selection of foodstus on the bench, labelled with the name of the food and TQSJOH its mass. Ask the students to decide which would provide the 1 J of energy needed to li the 1 N weight. e selection of foods and the masses of each will depend DIFNJDBMSFBDUJPO on local availability and the time of year, but one of the foods should be 1 mg OVDMFBSQPXFS (1/1000 g) of an orange, as this will provide approximately 1 J of energy. Grade 9 57 6OJU8PSLFOFSHZBOEQPXFS It is not possible to demonstrate experimentally that energy used and work done are equal as there is always some energy transferred as heat to the surroundings. I ,JOFUJDFOFSHZJG can, however, be shown that energy does work. Connect a small weight on the end USBWFMMJOHBUNT of a piece of thread to a small pulley wheel on the spindle of a 3–6 V toy electric L+ motor. Students can measure the voltage, current and time. ,JOFUJDFOFSHZJG energy used by the motor = voltage = current = time. USBWFMMJOHBUNT L+ Adjust the speed of the motor so that it takes a measurable time (about 2–3 s) to li the weight. It is best if the teacher tries this before showing the class and calculates the eciency of the motor. Activity 4.2: Answer Activity 4.3: Answer work done on weight 5PDPOGJSNGJOBMeciency = electrical energy supplied WFMPDJUZ When demonstrating the transfer of energy into mechanical work, inform the a = F/mNT students of the motor’s eciency. ey can then calculate the useful energy v = u as supplied (= electrical energy supplied = eciency) and the work done (= weight = vY height) and show they are approximately equal. Y Ask the students to provide examples of where they may see the dierent forms of v energy listed in the Students' Book. v NT It is worth examining the stopping distances for cars travelling at various speeds and reinforcing the dangers of excessive speed. e maximum speed limits are Activity 4.4: Answer 40 km/h within the city limits and 60 km/h outside. When a driver sees danger ahead, it takes time to react before braking and the car still moves forwards. e LHNBTTXPVME distance it travels is the thinking distance. While braking, the car is still moving OFFEUPCFN BCPWFUIFHSPVOE forwards. e distance travelled from the time the driver brakes until the car stops is the braking distance. e sum of these is the stopping distance. e thinking distance increases linearly with speed, but the braking distance is a &OFSHZTUPSFEJO squared relationship, because kinetic energy has to be transferred by the brakes and Activity 4.5: Answer 2 TUSFUDIFETQSJOHkinetic energy = ½mv 0.3 J so braking distance depends on the square of the velocity. e table shows the values up to 100 km/h. Vehicle inking speed (km/h) distance (m) 58 Braking distance (m) Stopping distance (m) 10 1.9 0.6 2.5 20 3.8 2.4 6.1 30 5.7 5.3 11.0 40 7.6 9.4 17.0 50 9.5 14.7 24.2 60 11.4 21.2 32.5 70 13.3 28.8 42.1 80 15.2 37.6 52.8 90 17.0 47.6 64.7 100 18.9 58.8 77.8 Grade 9 6OJU8PSLFOFSHZBOEQPXFS Ensure that students understand how to derive the equations for kinetic and gravitational potential energy. Revisit the work on stretching springs by examining a load–extension graph. e energy stored in a stretched spring is equal to the area under the graph. SA = starter activity MA = main activity CA = concluding activity Kinetic energy SA )BWFBTFMFDUJPOPGGPPETUVGGTMBCFMMFEXJUIOBNFPGGPPEBOENBTTPOUIFCFO TIPVMECFNHPGPSBOHFXIJDIXJMMQSPWJEF+PGFOFSHZ"TLTUVEFOUTUPEFDJEFXIJD XJMMQSPWJEF+PGFOFSHZOFFEFEUPMJGU/UISPVHIN MA "DUJWJUZ "DUJWJUZ CA %JTDVTTTUPQQJOHEJTUBODFTGPSDBST "DUJWJUZ Potential energy SA 8PSLJOTNBMMHSPVQTUPQSPEVDFMJTUPGTPVSDFTPGQPUFOUJBMFOFSHZ MA CA "DUJWJUZ "DUJWJUZoBMMPXTUVEFOUTUPQSPEVDFBMPBE¦FYUFOTJPOHSBQIGPSBTQSJOHXPS TNBMMHSPVQT 3FWJFXRVFTUJPOTUPCFEPOFXJUIBQBSUOFSUPFODPVSBHFEJTDVTTJPOBCPVUUIFT Activities t6TFHJWFOEBUBUPQMPUUIJOLJOHEJTUBODFBOECSBLJOHEJTUBODFGPSTQFFETVQUP 100 km/h. t6TFHSBQITGSPN)PPLFTMBXFYQFSJNFOUTUPDBMDVMBUFUIFFOFSHZTUPSFEJOB stretched spring. Resources http://webs.rps205.com/curriculum/science/les/ B394F7A6B21444F4816A38A22045D036.pdf Where next? e next section looks at how energy is conserved. As we are examining the law of conservation of energy, the need for all of us to conserve the natural energy resources of the planet on which we live is examined and suggestions made as to how this can be achieved locally. Answers to review questions 1. work done = change in energy W = Ek1 – Ek2 W = ½mv22 – ½mv12 W = ½m(v22 – v12) Grade 9 59 6OJU8PSLFOFSHZBOEQPXFS 2. a) 2400 J b) 240 J c) 240 kJ 3. Energy stored by a body which when released is capable of doing work; wound-up spring; stretched elastic band; parachutist about to leave the plane; water stored for a hydroelectric power station. 4. a) 900 J b) 2 m 5. 0.15 J 6. 114.4 J 5IJTTFDUJPO TIPVME $POTFSWBUJPOPGFOFSHZ GJMMBQQSPYJNBUFMZ 6 periods of Learning Competencies UFBDIJOHUJNF #ZUIFFOEPGUIJTTFDUJPOTUVEFOUTTIPVMECFBCMFUP t 4UBUFUIFMBXPGDPOTFSWBUJPOPGNFDIBOJDBMFOFSHZ Activity 4.6: Answer t 3FWJTFUIFUFSNDPMMJTJPOBOEEJTUJOHVJTICFUXFFOFMBTUJDBOEJO DPMMJTJPOT The football starts XJUIHSBWJUBUJPOBM t 4PMWFQSPCMFNTJOWPMWJOHJOFMBTUJDDPMMJTJPOTJOPOFEJNFOT QPUFOUJBMFOFSHZ MBXTPGDPOTFSWBUJPOPGNFDIBOJDBMFOFSHZBOENPNFOUVN as it falls it loses t &YQMBJOUIFFOFSHZDIBOHFTUIBUUBLFQMBDFJOBOPTDJMMBUJOHQFO HSBWJUBUJPOBM BOEBOPTDJMMBUJOHTQSJOHoNBTTTZTUFN QPUFOUJBMFOFSHZ BOEHBJOTLJOFUJD t %FTDSJCFUIFVTFPGFOFSHZSFTPVSDFTJODMVEJOHXJOEFOFSHZTPMB BOEHFPUIFSNBMFOFSHZ FOFSHZXIFOJUIJUT UIFHSPVOEUIFCBMMt &YQMBJOUIFNFBOJOHPGUIFUFSNSFOFXBCMFFOFSHZ EFGPSNTBOEHBJOT FMBTUJDQPUFOUJBM FOFSHZTPNFFOFSHZ is transformed into Starting off heat and sound is section introduces another physical quantity that is always conserved. Energy so the ball does cannot be created or destroyed – it is just transformed from one form to another. not rebound to its e term energy conservation is also applied to the problem the planet as a PSJHJOBMIFJHIU whole is facing as natural energy sources such as coal and oil are being depleted. Alternative energy sources must be utilised and everyone has a part to play in conserving the energy sources we have. Activity 4.7: Answer LHBUNTo NPNFOUVNLH Teaching notes NTLJOFUJDFOFSHZ Begin by asking the students to describe some common energy changes by either + naming a device and asking for the energy changes or providing the changes and LHBUNTo ask for the device that performs those changes. Examples might include: NPNFOUVNLH tMBNQFMFDUSJDBM¤ light (but a lot of energy is “lost” as heat) NTLJOFUJDFOFSHZ tNPUPSFMFDUSJDBM¤ kinetic + 60 Grade 9 6OJU8PSLFOFSHZBOEQPXFS tEZOBNPLJOFUJD¤ electrical Activity 4.8: Answer tQIPUPDFMMMJHIU ¤ electrical Before collision: tIZESPFMFDUSJDQPXFSTUBUJPOHSBWJUBUJPOBMQPUFOUJBM¤ electrical (in this .PNFOUVN example, there are some other energy transformations that take place between = mAvA + mBvB the water starting to fall and the electricity produced) = =9+ =9 tDMPDLTQSJOHFMBTUJDQPUFOUJBM¤ kinetic = LHNT tNJDSPQIPOFTPVOE¤ electrical ,JOFUJDFOFSHZ tCBUUFSZ DIFNJDBM¤ electrical = ½mAvA + ½mBvB =½==+ tDPBMDIFNJDBM¤ heat ½== It is important to stress that energy is not really “lost” during an energy =+ transformation. In any transformation of energy, there is always some energy that is not useful at the end of the transformation. It is still there, but cannot be usedAfter collision: .PNFOUVN for the intended purpose. A lamp works because the lament glows at a white hot = mAvA + mBvB temperature. = =3+ = James Joule was an English scientist whose name is given to the unit of energy. = LHNT While he was on honeymoon, he persuaded his wife, Amelia, to help him with an experiment. ey measured the temperature of water at the top and bottom of,JOFUJDFOFSHZ = ½mAvA + ½mBvB waterfalls in the Alps. Joule expected the temperature at the bottom of a waterfall = ½ = =9 + to be warmer as a result of energy transformation. ½== Revisit examples of collisions and ask students to identify examples of situations =+ in which most of the energy is conserved. Remember there is no such thing as$PMMJTJPO a JTFMBTUJO perfectly elastic collision. ere have been many designs put forward for energy transfer devices in which there is no energy wasted in the system. Such a device would carry on Activity 4.9: Answer GPTTJMGVFMT QMBOUT transforming energy for ever. is would be a perpetual motion machine, and animals such a machine would solve the world’s energy problems. QPXFS Dierent countries in the world rely on dierent energy sources. Ask the studentsOVDMFBS VSBOJVN GSPN&BSUI to look at Table 4.3 on pages 107–108 of the Students' Book and discuss why 8JOE4VO dierent energy sources are suitable for dierent countries. Why does Ethiopia use (FPUIFSNBM QSPDFTTFT so much hydroelectricity and not coal, for example? JOTJEF&BSUI )ZESPFMFDUSJDXBUFS 4PMBS4VO SA = starter activity MA = main activity CA = concluding activity Law of conservation of energy SA 4UVEFOUTXPSLJOTNBMMHSPVQTUPEFTDSJCFTPNFDPNNPOFOFSHZDIBOHFTTFFQBH MA "DUJWJUZ "DUJWJUZ CA 8JUIBQBSUOFSTUVEFOUTNBLFQPTUFSBCPVUMBXPGDPOTFSWBUJPOPGFOFSHZUPJ TUBUFNFOUPGMBXBOEFYBNQMFTPGBQQMJDBUJPOT Elastic and inelastic collisions SA 8PSLJOQBJSTUPMJTUFYBNQMFTPGFMBTUJDBOEJOFMBTUJDDPMMJTJPOT8IBUJTDP NBZDIBOHFJOFBDIDBTF MA "DUJWJUZ *OQBJSTQSBDUJTFDBMDVMBUJPOPGDPOTFSWBUJPOPGFOFSHZBOENPNFOUVNJOF CA 3FWJFXRVFTUJPO Grade 9 61 6OJU8PSLFOFSHZBOEQPXFS Energy in oscillating systems SA *OTNBMMHSPVQTTUVEFOUTUPFYQMPSFFYBNQMFTPGPTDJMMBUJOHTZTUFNTTVDIBT NBTT¦TQSJOHTZTUFNT MA *OBTNBMMHSPVQCVJMEBUPZDBSUIBUVTFTFMBTUJDCBOETBTUIFFOFSHZTPVSDF CA 4UVEFOUTUPXPSLXJUIBQBSUOFSUPNBLFUIFJSPXOTVNNBSZPG4UVEFOUTh#PPLQBHF ¦ Energy resources SA *OTNBMMHSPVQTMJTUBTNBOZFOFSHZSFTPVSDFTBTQPTTJCMF'FFECBDLJEFBT MA *OQBJSTSFTFBSDIPSJHJOTBOEVTFTPGGPTTJMGVFMT CA 1SFTFOUSFTVMUTPGSFTFBSDIJOGPSNPGQPTUFS Renewable energy SA 4UVEFOUTUPEJTDVTTXJUIBQBSUOFSXIBUUIFZVOEFSTUBOECZUIFUFSNASFOFXBCMF'F ideas. MA %JTDVTTJOTNBMMHSPVQTXIZEJGGFSFOUFOFSHZTPVSDFTJOUBCMFPOQBHFoPG4UV #PPLBSFTVJUBCMFGPSEJGGFSFOUDPVOUSJFT "DUJWJUZ CA 'FFECBDLJEFBTGSPNNBJOBDUJWJUZUPXIPMFDMBTT Energy in Ethiopia SA %JTDVTTBEWBOUBHFTBOEEJTBEWBOUBHFTPGIZESPFMFDUSJDQPXFSGPS&UIJPQJB MA 3FTFBSDIHFPUIFSNBMQPXFSHFOFSBUJPOJOTNBMMHSPVQT1SPEVDFBQSFTFOUBUJP CFOFGJUTBOEDPTUTGPSTVDIHFOFSBUJPOGPS&UIJPQJB CA 3FWJFXRVFTUJPOT¦XJUIBQBSUOFS Activities t1MPUHSBQITUPTIPXUIFSFMBUJPOTIJQTCFUXFFOLJOFUJDFOFSHZBOEW kinetic energy and mass, linear momentum and velocity, linear momentum and mass. t#VJMEBUPZDBSVTJOHFMBTUJDCBOETBTUIFFOFSHZTPVSDF t1SBDUJTFDBMDVMBUJPOTPGDPOTFSWBUJPOPGFOFSHZBOENPNFOUV collisions. t3FTFBSDIUIFQPTTJCMFTJUFTGPSHFPUIFSNBMQPXFSJO&UIJPQJB Resources http://library.thinkquest.org/C0110881/energy_en.html http://geothermal.marin.org/pwrheat.html Where next? e next section looks at mechanical power and how this is related to work and energy. ere are misconceptions that oen occur between the use of words such as strength, powerful and energetic. ese will need to be addressed. 62 Grade 9 6OJU8PSLFOFSHZBOEQPXFS Answers to review questions 1. e total energy of a closed system must remain constant. Energy is not 'lost'; it is transformed into another form of energy 2. velocity ball B: 6 m/s; inelastic; 12 J 3. a) 0.2 m b) 2.8 m/s or 3 m/s 4. energy sources that do not involve a fuel that will run out; any three from wind, wave, tide, geothermal, hydro, solar 5. water in upper lake, falls to drive water turbine, turbine turns generator, generator produces electricity; advantages – few greenhouse emissions, low running costs, can generate electricity very quickly if needed; disadvantages – large dams leads to environmental damage , can be expensive initial cost, cannot be built anywhere, problems if extended drought .FDIBOJDBMQPXFS Learning Competencies 5IJTTFDUJPO TIPVME GJMMBQQSPYJNBUFMZ 1 period of UFBDIJOHUJNF #ZUIFFOEPGUIJTTFDUJPOTUVEFOUTTIPVMECFBCMFUP t 4PMWFQSPCMFNTSFMBUJOHUPUIFEFGJOJUJPOPGQPXFS t 4IPXUIBUUIFL8IJTBMTPBVOJUPGXPSL t &YQSFTTUIFGPSNVMBPGNFDIBOJDBMQPXFSJOUFSNTPGBWFSBHFWFMPDJUZ Starting off is section builds on the study of work and energy by comparing the rate at which work is done or energy is used. A more powerful machine is able to do work faster and transfers its energy faster. Teaching notes Activity 4.10: Answer 4UVEFOUThPXO Begin by asking the students what they understand by the term powerful. ere is results some confusion between powerful, strong and energetic. Someone who is strong may not be powerful. A sumo wrestler is certainly very strong, but ask him to run up stairs quickly and it is obvious that he cannot transfer his energy very quickly. Activity 4.11: Answer His legs are not very powerful. 8+T Explain to students that power is the rate at which work is done or energy is 8T+ transferred. L8T+ Students can measure their own person power following the instructions in the L8I= Students’ Book. =+ Ask students to explain how two people, one very strong and muscular, the other L8I+ of slight build, can both have the same power developed in their legs when they climb the stairs. L8I.+ Grade 9 63 6OJU8PSLFOFSHZBOEQPXFS It is important that students realise that quantities oen have more than one unit. e power of a car engine is usually measured in horsepower rather than watts. Energy, too, is measured in dierent units. e kilowatt-hour is used when measuring domestic electricity consumption and power generation; the calorie (or kilocalorie) is still used by many as the unit for energy in foodstus, although this is being replaced by the joule and kilojoule on food labels. Explain how power can be calculated from a knowledge of work done (or energy transferred) and time taken or from a knowledge of force and velocity. SA = starter activity MA = main activity CA = concluding activity Mechanical power SA %JTDVTTNFBOJOHPGUFSNAQPXFSGVMXJUIBQBSUOFS'FFECBDLJEFBT MA "DUJWJUZ "DUJWJUZ CA 3FWJFXRVFTUJPOT &OEPGVOJURVFTUJPOT Activities t1SBDUJTFDBMDVMBUJPOTPGQPXFSXIFOEJFSFOUBNPVOUTPGXPSLBSF dierent amounts of time. Where next? e next unit looks at simple machines and how they are used to help us do work. Answers to review questions 1. power is a measure of the rate of doing work or transferring energy; watt (W); work done/time taken or force =velocity 2. a) 200 W b) 1000 W 3. a) 9 000 000 J b) 17 280 000 J 4. a) 2.5 kWh b) 4.8 kWh 5. P = work done/time taken = Fs/t = Fv 6. 200 000 W 64 Grade 9 6OJU8PSLFOFSHZBOEQPXFS Answers to end of unit questions 1. e total energy of a closed system must remain constant; work done by motor equals gain in gravitational potential energy of li. 2. 700 J 3. 1368 J 4. 4.5 kg 5. 22.5 J; 22.5 J 6. 0.2 J 7. a) 0.25 J b) 7.07 m/s c) 2.5 m 8. Spring compressed – elastic potential energy increases, kinetic energy decreases; spring stops – elastic potential energy at maximum, kinetic energy zero; spring stretches – elastic potential energy decreases, kinetic energy increases; spring at normal length – elastic potential energy zero, kinetic energy at maximum; spring stretches more – elastic potential energy increases, kinetic energy decreases; spring at maximum – elastic potential energy at maximum, kinetic energy zero; and so on. When vibrating vertically, kinetic energy is transferred into gravitational and elastic potential energy. 9. a) 2 m/s b) before 358 J, aer 22 J c) inelastic, energy not conserved 10.a) advantages – found in lots of places, relatively low cost, easily transported to power stations; disadvantages – non-renewable, mining is dangerous, produces greenhouse gases, transporting coal causes pollution b) advantages – produces few greenhouse emissions, can generate a lot of power; disadvantages – high capital building costs, only certain locations suitable c) advantages – relatively inexpensive, no greenhouse emissions; disadvantages – inconsistent supply, a lot of turbines needed to produce signicant amount of power 11.2000 J; 800 W 12.(200 = 10 = 7) / 6 = 2333 W = 2.33 kW 13.(10 000 = 10 = 50) / (60 = 5) = 16 667 W = 16.7 kW 14.300 = 10 = 10 = 30 000 J = 30 kJ; 30 000 / 5 = 6000 W = 6 kW 15.8000 N Grade 9 65 Simple machines Unit 5 Learning Competencies for Unit 5 This unit should GJMMBQQSPYJNBUFMZ By the end of this unit students should be able to: 11 periods of t &YQMBJOUIFQVSQPTFTPGBNBDIJOF UFBDIJOHUJNF t -JTUUIFUZQFTPGTJNQMFNBDIJOFT t %FUFSNJOFXIFUIFSUIFNBDIJOFTBSFGPSDFNVMUJQMJFSTTQFFENVMU PSEJSFDUJPODIBOHFST t %FGJOFUIFUFSNTMPBEFGGPSUXPSLPVUQVUXPSLJOQVUNFDIBOJDBM BEWBOUBHF."WFMPDJUZSBUJP73BOEFGGJDJFODZ t %FSJWFUIFFYQSFTTJPO = ."73GSPNJUTEFGJOJUJPO t %FSJWFBOFYQSFTTJPOGPS."PGBOJODMJOFEQMBOFXJUIPSXJUIPVUG t $BMDVMBUF."73BOEFGGJDJFODZPGBOJODMJOFEQMBOF t $BMDVMBUF."73BOEFGGJDJFODZPGBXFEHF t %FUFSNJOFUIF."73BOEFGGJDJFODZPGBMFWFS t *EFOUJGZUIFPSEFSTPGBMFWFSBOEHJWFFYBNQMFT t %FTDSJCFUIFVTFPGBXIFFMBYMFBOEEFUFSNJOF."73BOEFGGJDJFODZP XIFFMBOEBYMF t %FTDSJCFUIFVTFPGHFBST t %FTDSJCFEJGGFSFOUQVMMFZTZTUFNTBOEDBMDVMBUF."73BOEFGGJ QVMMFZTZTUFN t %FTDSJCFUIFVTFPGBKBDLTDSFX 5IJTTFDUJPO TIPVME 1VSQPTFTPGNBDIJOFT GJMMBQQSPYJNBUFMZ 1 period of Learning Competencies UFBDIJOHUJNF #ZUIFFOEPGUIJTTFDUJPOTUVEFOUTTIPVMECFBCMFUP t &YQMBJOUIFQVSQPTFTPGBNBDIJOF t -JTUUIFUZQFTPGTJNQMFNBDIJOFT t %FUFSNJOFXIFUIFSUIFNBDIJOFTBSFGPSDFNVMUJQMJFSTTQFFENVMU PSEJSFDUJPODIBOHFST t %FGJOFUIFUFSNTMPBEFGGPSUXPSLPVUQVUXPSLJOQVUNFDIBOJDBM BEWBOUBHF."WFMPDJUZSBUJP73BOEFGGJDJFODZ t %FSJWFUIFFYQSFTTJPO = ."73GSPNJUTEFGJOJUJPO 66 Grade 9 6OJU4JNQMFNBDIJOFT Starting off is topic introduces the idea of machines as devices that enable work to be done quicker and/or easier. It builds on the study of work and how the relative amounts of work done by the eort and the work done on the load are related by the eciency of the machine. Archimedes said: Give me a lever long enough and a fulcrum on which to place it, and I shall move the world. http://www.math.nyu.edu/~crorres/Archimedes/Lever/LeverIntro.html is one of many websites that have this picture. e whole unit can be very practical and does not need very much in the way of equipment. Teaching notes Activity 5.1: Answers It is worth spending a short time discussing the idea of what machines are and/." what they do. Ask students to list as many machines as they can think of. eir // list may include such things as a washing machine, sewing machine and rowing machine. Lead on to the idea that all of these machines make life easier and allow Activity 5.2: Answers us to do things quicker. N73 Start by showing the students a variety of machines, to include: N tMFWFSToBMMUISFFUZQFTPGMFWFSDMBTTXJUIUIFGVMDSVNJOUIFNNJEEMF DMBTT with the load in the middle and class 3 with the eort in the middle tJODMJOFEQMBOF tXFEHF tTDSFX tXIFFMBOEBYMF tQVMMFZoTJOHMFQVMMFZBOENVMUJQMFQVMMFZTZTUFNT Dene a machine as using an eort to move a load. Ask students to identify where the load is acting and where the eort is applied. Most of the machines are force multipliers; this means the eort is less than the load but the eort moves a greater distance than the load. Some are speed multipliers; this means the load moves a greater distance than the eort but the eort is greater than the load. Some machines change the direction in which a force acts. is makes it easier to apply the eort to the load. It is important to stress the dierence between work done and force used. Grade 9 67 6OJU4JNQMFNBDIJOFT Whenever a machine is used, the energy used is always greater than the work done on the load. However, the force used to move the load is usually less than the GPSDFFYFSUFECZUIFMPBE3FNJOETUVEFOUTPGUIFEFOJUJPOPGXPSLBOE UPFYQMBJOUIFDPOTFSWBUJPOPGFOFSHZFZTIPVMEUIJOLBCPVUXIFSFFO transferred into a non-useful form. is is usually in the form of heat, through friction, or it may be in a multiple-pulley system having to li the free pulley(s) as well as the load. Ask students to choose a machine for doing a particular job or identify the machine from household objects or pictures. &YBNQMFTNJHIUJODMVEFUIFGPMMPXJOH tMJJOHBOFOHJOFPVUPGBDBS QVMMFZT tSFNPWJOHUIFMJEGSPNBUJOPGQBJOU DMBTTMFWFS tHFUUJOHXBUFSGSPNUIFCPUUPNPGBXFMM XIFFMBOEBYMF tTIJOHSPE DMBTTMFWFS tXIFFMCBSSPX DMBTTMFWFS tTQMJUUJOHBMPH XFEHF tKBDLJOHVQBDBS TDSFX tSBNQUPQVTIBXIFFMCBSSPXJOUPBTLJQ JODMJOFEQMBOF Introduce the terms mechanical advantage and velocity ratio. Stress that because UIFTFBSFSBUJPTPGOVNCFSTXJUIUIFTBNFVOJUT."BOE73EPOPUIBWFVOJU themselves. ere are two forms of mechanical advantage. e ACTUAL mechanical advantage is what would be measured in the real world. e IDEAL mechanical advantage is a theoretical value assuming no energy losses. Introduce the term eciency. is too has no units. Show how to obtain the equation for eciency as eciency () = AMA 73 SA = starter activity MA = main activity CA = concluding activity Purposes of machines SA *OTNBMMHSPVQTEJTDVTTXIBUNBDIJOFTBSFBOEXIBUUIFZEP'FFECBDLJEFBT MA "DUJWJUZ "DUJWJUZ CA 3FWJFXRVFTUJPOTJOQBJST Activities t*EFOUJGZBMMPGUIFNBDIJOFTVTFEPOBCJDZDMF t1SBDUJTFDBMDVMBUJPOTPGNFDIBOJDBMBEWBOUBHFWFMPDJUZSBUJ t%JTDVTTUIFJNQMJDBUJPOTPGJOWFOUJOHBNBDIJOFJOXIJDIUIFBDUVB mechanical advantage and ideal mechanical advantage are the same. 68 Grade 9 6OJU4JNQMFNBDIJOFT Resources http://www.mikids.com/5machines.htm Where next? FOFYUTFDUJPOFYBNJOFTUIFJODMJOFEQMBOFXFEHFBOETDSFXJONPSFEFUBJM EFSJWJOHTQFDJDFYQSFTTJPOTGPSDBMDVMBUJOHUIF."BOE73GPSFBDI Answers to review questions MFWFSJODMJOFEQMBOFXFEHFTDSFX XIFFMBOEBYMFQVMMFZ FPSUJTGPSDFBQQMJFEUPBNBDIJOFMPBEJTGPSDFNPWFECZUIFNBDIJOFXPSL input is eort = distance moved by eort; work output is load = distance NPWFECZMPBE"."JTMPBEFPSU73JTEJTUBODFNPWFECZFPSUEJTUBODF NPWFECZMPBEFDJFODZJT."73*."JT."PGNBDIJOFJGOPFOFSHZJT MPTUJOUIFQSPDFTTBUIFPSFUJDBMWBMVFBTTVNJOHNBDIJOFJTFDJFOU B+ C+ D E F G 4. MA 9; load / *ODMJOFEQMBOFXFEHFBOETDSFX Learning Competencies 5IJTTFDUJPO TIPVME GJMMBQQSPYJNBUFMZ 5 periods of UFBDIJOHUJNF #ZUIFFOEPGUIJTTFDUJPOTUVEFOUTTIPVMECFBCMFUP t %FSJWFBOFYQSFTTJPOGPS."PGBOJODMJOFEQMBOFXJUIPSXJUIPVUGSJDUJPO t $BMDVMBUF."73BOEFGGJDJFODZPGBOJODMJOFEQMBOF t $BMDVMBUF."73BOEFGGJDJFODZPGBXFEHF Starting off is section builds on the denitions of mechanical advantage, velocity ratio and FDJFODZUPEFSJWFFYQSFTTJPOTTQFDJDUPUIFJODMJOFEQMBOFXFEHFBOETDSFX Teaching notes Start by showing the students the similarity between the inclined plane, wedge and screw. Grade 9 69 6OJU4JNQMFNBDIJOFT Activity 5.3: Answers Use some very long paper, such as wallpaper, and cut to the shape of an inclined plane. Mark the edge of the slope with either wide black felt marker or black tape. Attach the tallest end of the inclined plane to a cardboard cylinder about oDNEJBNFUFS/PXXJOEUIFJODMJOFEQMBOFBSPVOEUIFDZMJOEFSUPGPSN screw thread. To nish, add a square cap to the cylinder to make a bolt. Activity 5.4: Answers "." 73 5 &GG %JTDVTTFYBNQMFTPGJODMJOFEQMBOFTXFEHFTBOETDSFXT t8IZEPFTBSPBEHPJOHVQBNPVOUBJOHPJOB[JH[BHXJOEJOHCBDLPOJUTF IUUQMMDDPNCJLFJNBHFT8JOEJOH3PBEMBSHFKQHQSPWJEFTPOFFYBN t)PXEJEUIF&HZQUJBOTCVJMEUIFQZSBNJET t$VUUJOHUPPMTBSFFYBNQMFTPGXFEHFToDIJTFMQMBOFLOJGFBYFTBX the individual teeth), arrow, spear, nail. t4DSFXCPMUTKBDLTBMMVTFTDSFXUISFBETUPNBLFMJGFFBTJFS Derive the equations for mechanical advantage, velocity ratio and eciency for an inclined plane. Introduce the frictional forces involved and show how these are JODMVEFEXJUIJOUIFFYQSFTTJPOTPCUBJOFE %JTDVTTUIFEJFSFOUTIBQFTPGXFEHFTBOEEFSJWFFYQSFTTJPOTGPSNFD advantage, velocity ratio and eciency. Ask students to think about which shape PGXFEHFNBLFTUIFKPCFBTJFS"MPOHUIJOPOFPSBTIPSUXJEFPOF Ask students to decide whether a screw thread with a large pitch makes the job FBTJFSPSNPSFEJDVMU%FSJWFFYQSFTTJPOTGPSNFDIBOJDBMBEWBOUB ratio and eciency. 70 Grade 9 6OJU4JNQMFNBDIJOFT SA = starter activity MA = main activity CA = concluding activity Similarities between inclined plane, wedge and screw SA *OBTNBMMHSPVQFYQMPSFUIFTJNJMBSJUZCFUXFFOUIFJODMJOFEQMBOFUIFXFEHF TFFQBHF MA *OTBNFHSPVQTFYQMPSFFYBNQMFTPGJODMJOFEQMBOFTXFEHFTBOETDSFXT)PXEP NBLFMJGFFBTJFS CA *OTBNFHSPVQTSFTFBSDIIPX&HZQUJBOTCVJMUUIFQZSBNJET Inclined plane (1) SA MA 'FFECBDLSFTFBSDIGSPNFOEPGMBTUMFTTPO *OTNBMM HSPVQT DPNQBSF UIFGPSDF SFRVJSFE UPNPWF BOPCKFDU VQB SBNQ WFSTVT MJGUJOH JUUIF TBNFIFJHIUWFSUJDBMMZTFF'JHVSFJO4UVEFOUTh#PPL8IZBSFUIFSFTVMUTEJGGFSFO "DUJWJUZ CA 'VSUIFSFYBNQMFTPGDBMDVMBUJPOTPGNFDIBOJDBMBEWBOUBHFWFMPDJUZSBUJP BOJODMJOFEQMBOFUPCFUBDLMFEJOQBJST Inclined plane (2) SA *OTNBMMHSPVQTTUVEFOUTXSJUFEPXOFWFSZUIJOHUIFZDBOSFNFNCFSBCPVUGSJD MA "DUJWJUZ *OBTNBMMHSPVQNFBTVSFNFDIBOJDBMBEWBOUBHFWFMPDJUZSBUJPBOEFGGJDJFO PGJODMJOFEQMBOFTXJUIPVUBOEUIFOXJUIMVCSJDBUJPO)PXEPFTGSJDUJPOBGGFD 3FWJFXRVFTUJPOT¦ CA Wedge SA *OBTNBMMHSPVQUIJOLPGFYBNQMFTPGXFEHFTVTFEJOFWFSZEBZMJGF'FFECBDLJEF MA 8PSLXJUIBQBSUOFSUPTVNNBSJTFJOGPSNBUJPOPOXFEHFTJO4UVEFOUTh#PPLQBHF ¦ 8IJDITIBQFPGXFEHFNBLFTUIFKPCFBTJFTU 8IZ 3FWJFXRVFTUJPO CA Screw SA MA CA (JWFFBDIHSPVQPGTUVEFOUTBWBSJFUZPGTDSFXT5IFZTIPVMEPSEFSTDSFXTJOUFSN FBTZUIFZNBLFUIFKPCFBTJFTUUPIBSEFTU 8JUIBQBSUOFSNBLFBQPTUFSHJWJOHJOGPSNBUJPOBCPVUTDSFXTVTJOHQBHFPG4U #PPLBTBHVJEF %JTDVTTA5IJOLBCPVUUIJTPOQBHFPG4UVEFOUTh#PPLXJUIBQBSUOFS Activities t.FBTVSFNFDIBOJDBMBEWBOUBHFWFMPDJUZSBUJPBOEFDJFODZGPSBWBSJFUZPG supplied inclined planes, wedges and screws. t'JOEPVUIPXUIFFDJFODZPGBNBDIJOFDIBOHFTBTUIFMPBEJODSFBTFT Resources http://www.touregypt.net/construction http://en-wikipedia.org/wiki/wedge-(mechanical_device) Grade 9 71 6OJU4JNQMFNBDIJOFT Where next? FOFYUTFDUJPOFYBNJOFTMFWFSTHFBSTBOEQVMMFZTZTUFNTJONPSFEF EFSJWJOHTQFDJDFYQSFTTJPOTGPSDBMDVMBUJOHUIF."BOE73GPSFBDI Answers to review questions XPSLPVUQVUMPBE= h; work input = eort = l; work input = work output; MA = load / eort = l / h B C DN B/ C D 4. An inclined plane is stationary and eort is parallel to the slope; a wedge moves and eort is applied to the top of the wedge. 5IJTTFDUJPO TIPVME -FWFST GJMMBQQSPYJNBUFMZ 5 periods of Learning Competencies UFBDIJOHUJNF #ZUIFFOEPGUIJTTFDUJPOTUVEFOUTTIPVMECFBCMFUP t %FUFSNJOFUIF."73BOEFGGJDJFODZPGBMFWFS t *EFOUJGZUIFPSEFSTPGBMFWFSBOEHJWFFYBNQMFT t %FTDSJCFUIFVTFPGBXIFFMBOEBYMFBOEEFUFSNJOF."73BOEFGGJDJFO PGBXIFFMBOEBYMF t %FTDSJCFUIFVTFPGHFBST t %FTDSJCFEJGGFSFOUQVMMFZTZTUFNTBOEDBMDVMBUF."73BOEFGGJ QVMMFZTZTUFN t %FTDSJCFUIFVTFPGBKBDLTDSFX Starting off is section builds on the denitions of mechanical advantage, velocity ratio and FDJFODZUPEFSJWFFYQSFTTJPOTTQFDJDUPMFWFSTHFBSTBOEQVMMFZT Teaching notes Begin by asking the students to think about the see-saw in the playground when they were younger. While it is normal for two children of similar masses to play on the see-saw, very young children oen play with a parent. Ask how the parent can sit on the opposite side to the child without the child being permanently in the air. is should start the students thinking about load distance and eort distance. 72 Grade 9 6OJU4JNQMFNBDIJOFT 1SPWJEFFYBNQMFTPGEJFSFOUDMBTTFTPGMFWFSTFJUIFSJOUIFDMBTTSPPNPSCZ pictures showing the lever in action. Students should have the opportunity to use the lever and decide where the forces are acting and their direction; the position of the fulcrum and hence the class of lever. Suggested levers: tTFFTBX tDSPXCBSDBOCFDMBTTPSEFQFOEJOHPOIPXJUJTCFJOHVTFE tQMJFST tUPOHT tTDJTTPST tXIFFMCBSSPX tPBSNBOZXJMMUIJOLUIJTJTBDMBTTMFWFS tTQBEFDMBTTXIFOEJHHJOHCVUDMBTTXIFOTIJJOHUIFTPJM tTIJOHSPE tGPSFBSNMJJOHXFJHIUT tDMBXIBNNFS tUXFF[FST tCPUUMFPQFOFS Activity 5.5: Answer 4UVEFOUThPXO results Derive the equations for mechanical advantage, velocity ratio and eciency GPSBMFWFS4USFTTUIBUBDMBTTMFWFSDBOCFFJUIFSBGPSDFNVMUJQMJFSPSBTQFFE NVMUJQMJFSBDMBTTMFWFSJTBMXBZTBGPSDFNVMUJQMJFSBDMBTTMFWFSJTBMXBZTB speed multiplier. Ask students to think about why we use class 3 levers if the eort is greater than the load. e shing rod allowing the sherman to catch sh in the middle of the river without getting wet should provide the answer! 1SPWJEFFYBNQMFTPGXIFFMTBOEBYMFTFJUIFSJOUIFDMBTTSPPNPSCZQJDUVSFT TIPXJOHUIFXIFFMBOEBYMFJOBDUJPO4UVEFOUTTIPVMEIBWFUIFPQQPSUVOJUZUPVTF UIFXIFFMBOEBYMFBOEEFDJEFXIFSFUIFGPSDFTBSFBDUJOHBOEUIFJSEJSFDUJPO 4VHHFTUFEXIFFMTBOEBYMFT tXJOENJMM tCJDZDMFXIFFM tSPMMJOHQJO tTUFFSJOHXIFFM tUFMFQIPOFEJBM tEPPSLOPC tSFDPSEQMBZFS tTDSFXESJWFS tFHHXIJTL tTQBOOFS tGBJSHSPVOEXIFFM Derive the equations for mechanical advantage and velocity ratio for a wheel BOEBYMF"XIFFMBOEBYMFJTVTVBMMZBGPSDFNVMUJQMJFS*UNBZBDUBTBEJSFDUJPO changer. Ask students to suggest where gears can be found. e car or bicycle are the NPTUPCWJPVTFYBNQMFTCVUUIFSFBSFNBOZPUIFST$MPDLTIBWFHFBSTUIBUNBLF TVSFUIFIBOETUVSOBUUIFDPSSFDUSBUFoBTLTUVEFOUTIPXNBOZUJNFTGBTUFSUIF second hand goes round compared with the minute hand or the hour hand. Show TUVEFOUTFYBNQMFTPGEJFSFOUUZQFTPGHFBSBOEBTLUIFNUPJEFOUJGZUIFNBTGPSDF multipliers, speed multipliers or direction changers. Most gears will work both ways. e driving gear and driven gear can reverse their functions. However, the spur gear will only work one way. Grade 9 73 6OJU4JNQMFNBDIJOFT Activity 5.6: Answer 4UVEFOUThPXO results Gear types include: tTQVS tCFWFM tXPSNUIFXPSNJTUIFESJWJOHHFBSoJUDBOOPUCFESJWFO tIFMJDBM tSBDLBOEQJOJPO Derive the equations for mechanical advantage and velocity ratio for a pair of gears. 1SPWJEFFYBNQMFTPGQVMMFZTZTUFNT*UJTBEWJTBCMFUPIBWFUIFTFSFBEZ it takes time if the students try to thread them. Students should have the opportunity to use the pulleys and decide where the forces are acting and their direction. Derive the equations for mechanical advantage and velocity ratio for pulley systems. 'JOJTICZEJTDVTTJOH NPSFDPNQMFY NBDIJOFT TVDIBTEJFSFOUJBM QVMMFZT BOE jackscrews. SA = starter activity MA = main activity CA = concluding activity Using levers SA %JTDVTTTFFTBXTJOTNBMMHSPVQT)PXDBOBQBSFOUTJUPOUIFPQQPTJUFTJEFPGBTF BTNBMMDIJMEXJUIPVUUIFDIJMECFJOHQFSNBOFOUMZJOUIFBJS MA *OBTNBMMHSPVQDPOTUSVDUBMFWFSBOEVTFJUUPXPSLUISPVHI4UVEFOUTh#PPLQBH ¦ CA 8JUIBQBSUOFSNBLFBTVNNBSZPGXIBUIBTCFFOMFBSOUJOUIJTMFTTPO Different classes of lever SA MA 1SPWJEFFYBNQMFTPGEJGGFSFOUDMBTTFTPGMFWFSTFFQBHF4UVEFOUTTIPVMEXPS HSPVQTUPFYQMPSFFBDIMFWFSBOEEFDJEFXIFSFGPSDFTBSFBDUJOHBOEUIFJSEJSFD QPTJUJPOPGUIFGVMDSVNBOEIFODFUIFDMBTTPGMFWFS "DUJWJUZ CA 8JUIBQBSUOFSNBLFBQPTUFSTVNNBSJTJOHUIFEJGGFSFOUDMBTTFTPGMFWFS The wheel and axle SA MA CA 1SPWJEFFYBNQMFTPGXIFFMTBOEBYMFT4NBMMHSPVQTPGTUVEFOUTTIPVMEIBWFUIF UPVTFUIFXIFFMBOEBYMFBOEEFDJEFXIFSFUIFGPSDFTBSFBDUJOHBOEUIFJSEJSFDUJP *OBTNBMMHSPVQDPOTUSVDUBXIFFMBOEBYMFBTTIPXOJO'JHVSFPOQBHFPGUIF 4UVEFOUTh#PPL6TFUIJTNPEFMUPXPSLUISPVHIUIFUIFPSZ 3FWJFXRVFTUJPO Gears and pulleys SA *OTNBMMHSPVQTEJTDVTTXIFSFHFBSTDBOCFGPVOEJOFWFSZEBZMJGF'FFECBDLJEFB MA "DUJWJUZ CA 8JUIBQBSUOFSEFTJHOBQPTUFSBCPVUHFBSTBOEQVMMFZT More complex machines SA MA CA 74 (JWFTUVEFOUTBMJNJUFEUJNFUPXPSLXJUIBQBSUOFSUPXSJUFEPXOBTNBOZGBDUTB BCPVUNBDIJOFT *GQPTTJCMFBMMPXTUVEFOUTUPFYQMPSFEJGGFSFOUJBMQVMMFZTBOEKBDLTDSFX EJGGFSFOUJBMQVMMFZTBOEKBDLTDSFXTJOSFBMTJUVBUJPOT 4UVEFOUTXPSLJOQBJSTUPTVNNBSJTFXIBUUIFZIBWFMFBSOUJOUIJTVOJU Grade 9 6OJU4JNQMFNBDIJOFT Activities t%SBXQJDUVSFTPGWBSJPVTMFWFSTBOEBEEBSSPXTTIPXJOHUIFQPTJUJPOTPGMPBE eort and fulcrum and the directions in which the forces are acting. t%SBXQJDUVSFTPGWBSJPVTXIFFMTBOEBYMFTBOEBEEBSSPXTTIPXJOHUIF positions of load and eort and the directions in which the forces are acting. Resources http://en.wikipedia.org/wiki/dierential-pulley http://en.wikipedia.org/wiki/jackscrew Where next? FOFYUVOJUMPPLTBUTPNFQSPQFSUJFTPGVJETFTQFDJBMMZUIFQSFTTVSFFYFSUFECZ VJEBOEUIFSPMFPGBUNPTQIFSJDQSFTTVSFJOUFDIOPMPHZ Answers to review questions FEJTUBODFGSPNGVMDSVNUPFPSUJTHSFBUFSUIBOUIFEJTUBODFGSPNGVMDSVN to load. B/ b) 7.5 3. a) 5 C/ D "YFEQVMMFZJTBUUBDIFEUPPOFQPJOUXJUIBSPQFQBTTJOHPWFSUIFMPBEPOPOF end of the rope and eort on the other. "NPWBCMFQVMMFZIBTPOFFOEPGBSPQFYFEXJUIUIFMPBEBUUBDIFEUPUIF pulley, and the other end of rope has eort applied. "DPNQPVOEQVMMFZIBTBUPQQVMMFZYFEPOFFOEPGSPQFBUUBDIFEFJUIFS to top pulley or lower movable pulley load attached to movable pulley eort applied to the free end of rope. Answers to end of unit questions FSFJTBMXBZTTPNFFOFSHZUIBUJTOPUUSBOTGFSSFEJOUPVTFGVMFOFSHZCVUJT used to overcome friction, heat the surroundings or move the machine itself. GPSDFNVMUJQMJFSMPBEHSFBUFSUIBOFPSUXIFFMBOEBYMFXJUIMBSHFEJBNFUFS XIFFMUVSOJOHTNBMMEJBNFUFSBYMFTUFFSJOHXIFFM speed multiplier; eort greater than load; lever with distance from fulcrum to load greater than distance from fulcrum to eort; shing rod direction changer; direction of eort dierent to direction of load; worm gear; DIBOHFTEJSFDUJPOPGSPUBUJPOCZ¡ Grade 9 75 6OJU4JNQMFNBDIJOFT B¡ b) 3 D/ LOJGFBYFEPPSTUPQBSSPX TQFBSTXPSEOBJM 5. a) 5 C/ 6. e thread is an inclined plane wrapped around a cylinder. DMBTToGVMDSVNJONJEEMFoDMBXIBNNFSTFFTBX CBMBODF DMBTToMPBEJONJEEMFoXIFFMCBSSPX CPUUMFPQFOFSPBS DMBTToFPSUJONJEEMFoTIJOHSPEUXFF[FSTUPOHT 8. A lever is used to turn a screw thread. *."73EJTUBODFUSBWFMMFECZMFWFSEJTUBODFUSBWFMMFECZTDSFXU @r / p (where r is length of lever and p is pitch of screw) 76 Grade 9 Fluid statics Unit 6 This unit should GJMM BQQSPYJNBUFMZ By the end of this unit students should be able to: 12 periods of t %FGJOFUIFUFSNBJSQSFTTVSFBOEVTFUIFEFGJOJUJPOUPTPMWFSFMBUFE UFBDIJOHUJNF QSPCMFNT Learning Competencies for Unit 6 t %FTDSJCFBUNPTQIFSJDQSFTTVSFBOEFYQMBJOJUTWBSJBUJPOXJUIBMUJUVEF t &YQMBJOIPXUPNFBTVSFBUNPTQIFSJDQSFTTVSFBOETIPXUIBUNN)HJT FRVBMUPPOFBUNPTQIFSF t %FGJOFUIFUFSNGMVJEBOETUBUFUIFTJNJMBSJUJFTBOEEJGGFSFODFTCFUXFFO MJRVJETBOEHBTFT t %FGJOFUIFUFSNEFOTJUZBOESFMBUJWFEFOTJUZBOEEFUFSNJOFFBDIGPSB HJWFOCPEZ t &YQMBJOIPXUIFQSFTTVSFJOBMJRVJEBUSFTUWBSJFT t "QQMZUIFGPSNVMBp = hgBOEVTFJUUPTPMWFQSPCMFNTJODMVEJOH EFUFSNJOJOHUIFQSFTTVSFJOTJEFBGMVJEUBLJOHJOUPBDDPVOUBUNPTQIFSJD QSFTTVSF t 4UBUF1BTDBMTQSJODJQMFBOEBQQMZJUUPTPMWFQSPCMFNTBOEFYQMBJO BQQMJDBUJPOTTVDIBTUIFIZESBVMJDMJGU t &YQMBJOUIFVTFPGBNBOPNFUFS t %FNPOTUSBUFBOVOEFSTUBOEJOHPGEJTUJOHVJTICFUXFFOBOEDBMDVMBUF BUNPTQIFSJDHBVHFBOEBCTPMVUFQSFTTVSF t 4UBUF"SDIJNFEFTTQSJODJQMFBOEUIFQSJODJQMFPGGMPUBUJPO t %JTUJOHVJTICFUXFFOUSVFXFJHIUBOEBQQBSFOUXFJHIUPGBCPEZ t $BMDVMBUFUIFCVPZBOUGPSDFBDUJOHPOUIFCPEZJOBGMVJEBOEFYQMBJOXIZ CPEJFTGMPBUPSTJOL t $BMDVMBUFUIFEFOTJUZPGBGMPBUJOHCPEZPSEFOTJUZPGBGMVJEVTJOHUIF GMPUBUJPOQSJODJQMF "JSQSFTTVSF Learning Competencies 5IJTTFDUJPO TIPVME GJMMBQQSPYJNBUFMZ 5 periods of UFBDIJOHUJNF #ZUIFFOEPGUIJTTFDUJPOTUVEFOUTTIPVMECFBCMFUP t %FGJOFUIFUFSNBJSQSFTTVSFBOEVTFUIFEFGJOJUJPOUPTPMWFSFMBUFE QSPCMFNT t %FTDSJCFBUNPTQIFSJDQSFTTVSFBOEFYQMBJOJUTWBSJBUJPOXJUIBMUJUVEF t &YQMBJOIPXUPNFBTVSFBUNPTQIFSJDQSFTTVSFBOETIPXUIBUNN)HJT FRVBMUPPOFBUNPTQIFSF Grade 9 77 6OJU'MVJETUBUJDT Starting off is topic deals with the pressure exerted by the air and how air pressure is measured. It is important that students realise the dierence between force and pressure. Place three identical bricks on the table each with a dierent face (area) in contact with the table. e bricks all have the same weight so exert the same force on the table. But the brick placed with the smallest surface area exerts the most pressure. e one with the largest face in contact exerts the least pressure. Activity 6.1: Answers 2 p/N F/ AN Teaching notes Show students a photograph of an elephant and of a girl wearing stiletto-heeled shoes. 2 Ask students to imagine being walked on by the elephant and the girl. Which would be preferable? Use this example to introduce the idea of pressure as force/area. Activity 6.2: Answer 4UVEFOUThPXO results A typical African elephant has a mass of 4000 kg. e girl has a mass of 50 kg. e weight of the elephant is 40 000 N, 10 000N on each foot. e weight of the girl is 500 N, 250 N on each foot. Activity 6.3: Answer . e area of the stiletto heel is e area of each of the elephant’s feet is 10002cm 1 cm2. 4UVEFOUThPXO results An elephant lands the whole surface area of its foot as it walks, so each foot exerts 2. a pressure of 10 000/1000 or 10 N/cm e girl will put her weight on the heel as she walks, so the stiletto heel exerts a 2. pressure of 250/1 or 250 N/cm Although the elephant is 80 times heavier, the pressure from the heel is 25 times greater. Ask students to think about how pressures are high or low in the following examples: tQVTIJOHJOBNBQQJOoTNBMMBSFB tIBNNFSJOHJOBOBJMoMBSHFGPSDFBOETNBMMBSFB tTFXJOHXJUIBOFFEMFoTNBMMBSFB tDBUFSQJMMBSUSBDLTPOBWFIJDMFoMBSHFBSFB tBDBNFMTXFCCFEGFFUoMBSHFBSFB tTLJToMBSHFBSFB 78 Grade 9 6OJU'MVJETUBUJDT Introduce the idea of air pressure by asking what is all around us and whether it has mass. Ask whether the atmosphere stretches for ever or whether it has a nite height. e mass of the air above us covering a 12 area m is about 10 100 kg. is Discuss the causes of results in atmospheric pressure being about 101 0002. N/m air pressure, leading the students to think at a particle level. Discuss what happens to air pressure as the height above the ground increases. Activity 6.4: Answer 35 000 30 000 Altitude (m) 25 000 20 000 15 000 10 000 5000 0 11 0 00 0 00 0 00 0 00 0 00 0 00 0 00 0 00 0 00 0 00 0 00 0 10 90 80 70 60 50 40 30 20 10 0 Atmospheric pressure (Pa) Place a strip of wood overhanging the edge of a table and cover the end on the Activity 6.5: Answer table with a large sheet of at newspaper. Strike the overhanging end of the wood sharply. e wood should snap. e pressure of the air is acting over a large area. 4UVEFOUThPXO When the wood is struck, the covered end moves up slightly and all of the force is results concentrated onto the wood so it snaps. Air pressure does not just act vertically downwards. e air particles are moving in all directions and pushing on every surface they come into contact with. Use a sucker and place it carefully against a glass window. It falls o. Now push the sucker onto the window and it stays there. ere is no air between the sucker and the window to push the sucker o the window, but there is air in the room pushing against the sucker. Ask students why our bodies do not collapse under atmospheric pressure. Activity 6.6: Answer e Magdeburg hemispheres can be demonstrated quite eectively using two clean, new sink plungers. *OBWBDVVN 1. Put the two plungers together; ask one student to put a nger in between DMFBOFSUIFGBO them. DBVTFTQSFTTVSF 2. Push the plungers together to squeeze out as much air as possible. ESPQJOTJEFUIF 3. e student removes their nger; make sure the seal between the plungers isWBDVVNDMFBOFSUIF air outside enters tight. UIFSFHJPOPGMPXFS 4. Ask two students to pull the plungers apart; make sure there is someone to QSFTTVSFCFGPSF catch them before they fall over! CFJOHFYQFMMFE Introduce the barometer as the instrument used for measuring atmospheric DBSSZJOHEJSUXJUI pressure. Compare the densities of mercury air and water to explain why JUEJSU JOUIFDBSQFU atmospheric pressure is quoted as 760 mmHg and why water is not used instead. JTCSVTIFETDSBQFE Ask students why they cannot use a drinking straw 15 m long out of a h oor JOUPUIFQBUIPG window to drink from a glass on the ground below. NPWJOHBJS Ask students to consider the uses of atmospheric pressure. Grade 9 79 6OJU'MVJETUBUJDT SA = starter activity MA = main activity CA = concluding activity Under pressure SA 4UVEFOUTEJTDVTTJOTNBMMHSPVQTXIFUIFSJUXPVMECFQSFGFSBCMFUPCFXBMLFEP FMFQIBOUPSBHJSMJOTUJMFUUPIFFMT'FFECBDLJEFBTXJUISFBTPOJOH MA "DUJWJUZ "DUJWJUZ CA 4UVEFOUTEJTDVTTXJUIBQBSUOFSXIFUIFSQSFTTVSFJTIJHIPSMPXJOFYBNQMFTHJWFO PGUIJTCPPL Atmospheric pressure (1) SA 4UVEFOUTEJTDVTTXJUIBQBSUOFSUIFDBVTFTPGBJSQSFTTVSF'FFECBDLJEFBT MA "DUJWJUZ CA 8PSLXJUIBQBSUOFSUPTVNNBSJTF4UVEFOUTh#PPLQBHFT¦ Atmospheric pressure (2) SA 4UVEFOUTUPEJTDVTTXJUIBQBSUOFSXIFSFNFBTVSFNFOUTPGBUNPTQIFSJDQSFTTVSF FWFSZEBZMJGFXFBUIFSGPSFDBTUT MA "DUJWJUZ CA 4UVEFOUTUPXPSLJOQBJSTUPSFTFBSDICBSPNFUFSTBOEGJOEPVUXIZNNPGNFSDVSZ HFOFSBMMZVTFEJOBCBSPNFUFS Uses of air pressure (1) SA 4UVEFOUTUPXPSLJOTNBMMHSPVQTUPFYQMPSFTVDUJPOQBETBOEESJOLJOHTUSBXT MA &YQMPSF.BHEFCVSHIFNJTQIFSFTTFFQBHFPGUIJTCPPLJOTNBMMHSPVQT CA 4UVEFOUTXPSLXJUIBQBSUOFSUPQSPEVDFBQPTUFSUPFYQMBJOIPXMJGUQVNQTBOE XPSL Uses of air pressure (2) SA 4UVEFOUTUPXPSLJOTNBMMHSPVQTUPFYQMBJOIPXCJDZDMFQVNQTXPSL MA "DUJWJUZ "DUJWJUZ CA 3FWJFXRVFTUJPOT¦ Activities t1SBDUJTFDBMDVMBUJPOTPGQSFTTVSF t4UVEFOUTDBODBMDVMBUFUIFJSPXOQSFTTVSFVTJOHHSBQIQBQFSUPO area and weighing machine to nd their weight in N. Resources http://en.wikipedia.org/wiki/Barometer Where next? e next section examines pressure in uids; this means in gases as well as liquids. e transfer of pressure through liquids has many uses and these are examined in some detail. e section also explains why some objects that are made of dense materials such as steel oat on water. 80 Grade 9 6OJU'MVJETUBUJDT Answers to review questions 2 or Pa 1. force acting per unit area; N/m 2. maximum 1000 Pa; minimum 333.3 Pa 3. Air pressure is air particles exerting a force on a surface; higher altitude means less air above pushing down. 4. Mercury pushes down inside the barometer tube, which balances air pushing down in trough. 2 weight of 760 mm column mercury = 9.81(0.760 × density)r 2 = 9.81(0.760 × 13 570)r= 101 000 r2 N; 2/rr 2 = 101 000 Pa pressure = force/area = 101 000 5. 108 973 Pa 'MVJEQSFTTVSF Learning Competencies 5IJTTFDUJPO TIPVME GJMMBQQSPYJNBUFMZ 7 periods of UFBDIJOHUJNF #ZUIFFOEPGUIJTTFDUJPOTUVEFOUTTIPVMECFBCMFUP t %FGJOFUIFUFSNGMVJEBOETUBUFUIFTJNJMBSJUJFTBOEEJGGFSFODFTCFUXFFO MJRVJETBOEHBTFT t %FGJOFUIFUFSNEFOTJUZBOESFMBUJWFEFOTJUZBOEEFUFSNJOFFBDIGPSB HJWFOCPEZ t &YQMBJOIPXUIFQSFTTVSFJOBMJRVJEBUSFTUWBSJFT t "QQMZUIFGPSNVMBp = hgBOEVTFJUUPTPMWFQSPCMFNTJODMVEJOH EFUFSNJOJOHUIFQSFTTVSFJOTJEFBGMVJEUBLJOHJOUPBDDPVOUBUNPTQIFSJD QSFTTVSF t 4UBUF1BTDBMTQSJODJQMFBOEBQQMZJUUPTPMWFQSPCMFNTBOEFYQMBJO BQQMJDBUJPOTTVDIBTUIFIZESBVMJDMJGU t &YQMBJOUIFVTFPGBNBOPNFUFS t %FNPOTUSBUFBOVOEFSTUBOEJOHPGEJTUJOHVJTICFUXFFOBOEDBMDVMBUF BUNPTQIFSJDHBVHFBOEBCTPMVUFQSFTTVSF t 4UBUF"SDIJNFEFTTQSJODJQMFBOEUIFQSJODJQMFPGGMPUBUJPO t %JTUJOHVJTICFUXFFOUSVFXFJHIUBOEBQQBSFOUXFJHIUPGBCPEZ t $BMDVMBUFUIFCVPZBOUGPSDFBDUJOHPOUIFCPEZJOBGMVJEBOEFYQMBJOXIZ CPEJFTGMPBUPSTJOL t $BMDVMBUFUIFEFOTJUZPGBGMPBUJOHCPEZPSEFOTJUZPGBGMVJEVTJOHUIF GMPUBUJPOQSJODJQMF Starting off is section builds on the study of atmospheric pressure by considering the pressure in uids. It is important that students realise that as well as liquids, all gases are considered to be uids. Density is an important physical quantity that is related to pressure and allows us to calculate the pressure due to a column of Grade 9 81 6OJU'MVJETUBUJDT uid without having to calculate its mass and weight. Forces in uids are also examined, providing an explanation as to why dense objects, such as steel, can oat on water. Activity 6.7: Answer Teaching notes )H Begin by asking the students what they understand by the term uid. Most are likely to describe liquids. Anything that can ow along a pipe or pour from a container is a uid. Show students that water is a uid by pouring it from one beaker to another. To show that a gas is a uid, place a lit night-light in the bottom of one beaker. In a second beaker place a small quantity of dry ice (solid carbon dioxide). You will need to be careful when holding this beaker as it will be very cold. Use very thick gloves to hold it. Once the dry ice starts to warm up, clouds of carbon dioxide gas will be visible. Pour this gas from one beaker to the other. Since carbon dioxide is denser than air, it will pour downwards into the beaker containing the night-light. e night-light will be extinguished. If you have access to a cylinder of carbon dioxide, this can be used to ll one beaker instead of using dry ice. Alternatively, carbon dioxide can be formed when an acid such as hydrochloric acid reacts with a metal carbonate such as calcium carbonate. e resulting gas can be collected in a boiling tube or beaker and poured onto the night-light. $02 1FUSPM )POFZ Activity 6.8: Answer 4UVEFOUThPXO results Activity 6.9: Answer 4UVEFOUThPXO results Activity 6.10: Answer EJWFL1B Discuss the main dierence between a gas and BMJRVJEoBHBTDBOCFDPNQSFTTFECVUBMJRVJE cannot. is is important when the transmission of pressure is considered later. NFSDVSZDPMVNO Explain how to calculate density and what eect L1B the height above the Earth’s surface has on the h density of a liquid (none) and a gas (decreases as height increases). Show students the eect of depth on liquid pressure using a tall tin can with holes at dierent depths. Use this to explain why dams for reservoirs increase in thickness as the reservoir depth increases. X Water Connect a rubber tube to one end of a manometer. Attach a thistle funnel or similar to the other end of the tube and cover with a piece of rubber (from a balloon) or cling lm. When this free end is placed in a tall container of water, the height, h, increases as the funnel gets lower in the water. is is showing that pressure increases with depth. If the rubber tubing is connected very close to the funnel (X in the diagram on the right), the funnel can be turned so that it faces horizontally or upwards. e reading, h, on the manometer does not change. is shows that pressure acts equally in all directions. Show students how to derive the expression p = hg and provide them with opportunities to solve problems using this expression. Remind them that when diving, for example, the total pressure acting is the sum of the water pressure and the atmospheric pressure. 82 Grade 9 6OJU'MVJETUBUJDT To show students the dierence between compressible and incompressible uids, join together two syringes of dierent diameters with a length of rubber tubing. It is important that the tubing is a tight t on the syringes if students are not to get very wet! Activity 6.11: Answer A B 4UVEFOUThPXO results Activity 6.12: Answer Start with the syringes full of air. Ask one student to hold syringe A while another 4UVEFOUThPXO pushes and pulls the plunger of syringe B. e plunger of syringe A will move results in and out as well. If the student now tries to stop the plunger of syringe A from moving, this can be done easily, as the gas is compressible. Reverse the roles and Activity 6.13: the same thing happens. Answer Fill the syringes with water and repeat the experiment. When the plungers are free to move, they will do so with ease, but when restricted the student holding4UVEFOUThPXO in plunger B will not be able to do so when plunger A is pushed in. When the results student tries to push in plunger B against plunger A being held, they will not be able to do so. Pressure is being transmitted through the liquid because it is Activity 6.14: incompressible. A small force acting over a small area (A) is balanced by a large Answer force acting over a large area (B). If there is a large force acting on A, then it would 4UVEFOUThPXO need a very large force acting on B to balance it. Explain that this is the principle results of the hydraulic li. Students will already have seen a mercury barometer or a picture of one; most household barometers use the aneroid barometer. A manometer was introduced at the start of this section; use a party blower to show the principle of the Bourdon gauge. Introduce buoyant forces by trying to oat a steel block on water. It sinks. Attach the block to a newtonmeter and lower it into the water. e weight appears to decrease. Finally repeat with a hollowed out piece of steel or a steel sheet bent to the shape of a boat. e steel oats and its apparent weight is zero. If possible use a piece of steel with the same mass as the original block to make it a fair test. Discuss the implication of oating objects, such as boats, and introduce the plimsoll line. Students can verify Archimedes's principle and the principle of otation using everyday objects attached to a newtonmeter and either displacing water from a eureka can into a measuring cylinder or immersing the object in a measuring 3, the cylinder and noting the rise in water level. As the density of water is 1 g/cm mass of water displaced is numerically equal to the volume. SA = starter activity MA = main activity CA = concluding activity What are fluids? SA 4UVEFOUTEJTDVTTXJUIBQBSUOFSXIBUUIFZVOEFSTUBOECZUIFUFSNAGMVJE'FFECBD MA "DUJWJUZ "DUJWJUZ CA 4UVEFOUTXPSLXJUIBQBSUOFSUPTVNNBSJTFMFBSOJOHGSPNUIJTMFTTPO Grade 9 83 6OJU'MVJETUBUJDT Pressure in fluids SA 4UVEFOUTEJTDVTTGPMMPXJOHRVFTUJPOTXJUIBQBSUOFSA)PXEPFTUIFQSFTTVSFJOB XJUIEFQUI BEFDSFBTFCTUBZUIFTBNFDJODSFBTF MA "DUJWJUZ "DUJWJUZ "DUJWJUZ CA *OQBJSTTUVEFOUTSFTFBSDIBQQMJDBUJPOTPGUIFQSJODJQMFTMFBSOUJOUIJTMFTT UIJDLFSBUUIFCPUUPNUIBOUIFUPQSFBEZUPGFFECBDLBUTUBSUPGOFYUMFTTPO Pascal’s principle SA 'FFECBDLGSPNSFTFBSDIBUFOEPGMBTUMFTTPO MA "DUJWJUZ CA 4UVEFOUTXPSLJOTNBMMHSPVQTUPSFTFBSDIBQQMJDBUJPOTPG1BTDBMTQSJODJQM Hydraulic machines SA 'FFECBDLGSPNSFTFBSDIBUFOEPGMBTUMFTTPO MA "DUJWJUZ CA 8PSLXJUIBQBSUOFSUPTVNNBSJTFUIFEJGGFSFODFTCFUXFFOBUNPTQIFSJDHBVHFBOE QSFTTVSF Measuring pressure SA 4UVEFOUTXPSLJOQBJSTUPFYQMBJO'JHVSFPOQBHFPG4UVEFOUTh#PPLJOUIFJSPXO XPSET MA 8PSLXJUIBQBSUOFSUPQSFQBSFBQSFTFOUBUJPOPONFDIBOJDBMUFDIOJRVFTGPSNFB QSFTTVSF CA 4UVEFOUTHJWFQSFTFOUBUJPOT Forces in fluids SA 8PSLXJUIBQBSUOFSUPNFBTVSFUIFCVPZBOUGPSDFBDUJOHPOBTUPOFTFF'JHVSFPO QBHFPG4UVEFOUTh#PPL MA "DUJWJUZ CA 8JUIBQBSUOFSTVNNBSJTFQBHFT¦PG4UVEFOUTh#PPL Floating and sinking SA *OBTNBMMHSPVQFYQMPSFPCKFDUTGMPBUJOHBOETJOLJOH"UUBDIUIFPCKFDUTUPBO BOEPCTFSWFIPXUIFXFJHIUDIBOHFTBTUIFZIJUUIFXBUFS MA *OBTNBMMHSPVQEFWJTFBOFYQFSJNFOUUPWFSJGZUIFQSJODJQMFPGGMPUBUJPO CA 3FWJFXRVFTUJPOT &OEPGVOJURVFTUJPOT Activities t1SBDUJTFDBMDVMBUJOHUIFEFOTJUZPGSFHVMBSTIBQFETPMJETBOEM containers either from given data or from the student’s own measurements. t1SBDUJTFVTJOHUIFFRVBUJPOp = hg. t6TFBUJODBOXJUIIPMFTBSPVOEJUKVTUBCPWFUIFCBTFUPTIPXUIBUQSFT acts equally in all directions. t7FSJGZ"SDIJNFEFThTQSJODJQMFBOEUIFQSJODJQMFPGPUBUJPO 84 Grade 9 6OJU'MVJETUBUJDT Resources http://en.wikipedia.org/wiki/Pressure_measurement Answers to review questions BVJEPXTBMPOHBQJQFoBOZMJRVJEPSHBTXBUFSoBJSoPJMoOBUVSBMHBTo any named gas or liquid 2. 1020 kPa; 1121 kPa 3. e pressure applied to an enclosed uid is transmitted to every part of the uid, as well as to the walls of the container without reducing in value; hydraulic li. 4. a) 1000 Pa; 2000 N b) 6000 Pa; 300 N 5. a) buoyant force = weight b) buoyant force < weight c) buoyant force > weight Answers to end of unit questions 1. 100 kPa 2. Particles are moving in all directions. ey collide with the walls of the container. ey exert of force over an area. 3. Similarities between liquids and gases are that they ow through pipes and pour from one container to another. A dierence is that liquids cannot be compressed but gases can. 4. 10.1 m 5. Absolute pressure is total pressure acting at a point. Atmospheric pressure is pressure of surrounding air acting at a point on the Earth’s surface. Gauge pressure is pressure dierence between a system and atmospheric pressure. 6. If a manometer is connected to a gas supply you can note the height dierence between the two levels. Pressure is 1500 Pa. 7. Any object, wholly or partially immersed in a uid, is buoyed up by a force equal to the weight of the uid displaced by the object. A oating body displaces its own weight of the uid in which it oats. 8. e boat needs to displace a greater weight of water to allow it to still oat. 9. e buoyant force is 3.0 N so it sinks. 10.136 kg/m3; 51 000 000 kg; It oats because it has a relative density of less than 1. Grade 9 85 Temperature and heat Unit 7 5IJTVOJUTIPVME Learning Competencies for Unit 7 GJMMBQQSPYJNBUFMZ By the end of this unit students should be able to: 12 periods of t &YQMBJOUIFEJGGFSFODFCFUXFFOIFBUBOEUFNQFSBUVSF UFBDIJOHUJNF t %FGJOFUIFUFSNUIFSNBMFRVJMJCSJVN t %FTDSJCFUIFUIFSNBMFYQBOTJPOPGTPMJETBOEEFSJWFUIFFYQSFTTJ MJOFBSBOETVSGBDFFYQBOTJPOPGTPMJET t 'JOEUIFSFMBUJPOTIJQCFUXFFOUIFDPFGGJDJFOUTPGMJOFBSBSFBBOE FYQBOTJPOBOETPMWFSFMBUFEQSPCMFNT t ,OPXBQQMJDBUJPOTPGUIFUIFSNBMFYQBOTJPOPGNBUFSJBMT t %JTUJOHVJTICFUXFFOBQQBSFOUBOESFBMFYQBOTJPOPGBMJRVJEBO QSPCMFNTJOWPMWJOHUIFFYQBOTJPOPGMJRVJET VTJOHV = V oT t &YQMBJOUIFBCOPSNBMFYQBOTJPOPGXBUFS t $PNQBSFUIFFYQBOTJPOPGHBTFTXJUIUIFFYQBOTJPOPGTPMJEBOEMJR t %FTDSJCFUIFGBDUPSTUIBUBGGFDUUIFBNPVOUPGIFBUBCTPSCFEPSM CZBCPEZ t %FGJOFUIFUFSNTTQFDJGJDIFBUDBQBDJUZBOEIFBUDBQBDJUZBOEDB UIFBNPVOUPGIFBUFOFSHZBCTPSCFEPSMJCFSBUFECZBCPEZVTJOH Q = mc∆T t $BMDVMBUFUIFIFBUDBQBDJUZPGBCPEZ t *EFOUJGZEJGGFSFOUVOJUTPGIFBUFOFSHZ t &YQMBJOUIFTJHOJGJDBODFPGUIFIJHITQFDJGJDIFBUDBQBDJUZPGXBU t 6TFUIFSFMBUJPOTIJQIFBUMPTUIFBUHBJOFEUPTPMWFQSPCMFNTJOWP IFBUFYDIBOHF t %FTDSJCFUIFVTFTPGBDBMPSJNFUFS t %FGJOFUIFUFSNTMBUFOUIFBUMBUFOUIFBUPGGVTJPOBOEMBUFOUIFB WBQPSJTBUJPO t 4PMWFQSPCMFNTJOWPMWJOHDIBOHFPGTUBUF 5IJTTFDUJPO TIPVME 5FNQFSBUVSFBOEIFBU GJMMBQQSPYJNBUFMZ 2 periods of UFBDIJOHUJNF Learning Competencies #ZUIFFOEPGUIJTTFDUJPOTUVEFOUTTIPVMECFBCMFUP t &YQMBJOUIFEJGGFSFODFCFUXFFOIFBUBOEUFNQFSBUVSF t %FGJOFUIFUFSNUIFSNBMFRVJMJCSJVN 86 Grade 9 6OJU5FNQFSBUVSFBOEIFBU Starting off is topic deals with temperature as a measure of the hotness of a body on a chosen scale and heat as a form of energy on an absolute scale. ere are many temperature scales, some of which are not always evident. We do not use a laboratory thermometer before deciding on how long to stay in the bath or whether to put a scarf on when we go outside. Our skin acts as a thermometer and makes the appropriate measurement. Teaching notes Activity 7.1: Answer It is worth spending a short time discussing the dierence between temperature$FMTJVTUP,FMWJO and heat. Start with a beaker of water and heat it with a constant source of heat. BEE Record the temperature every half minute. e temperature rises until it reaches ,FMWJOUP$FMTJVT 100°C. Continue to heat the water for a few minutes and note that the temperature TVCUSBDU no longer rises. Heat is still being supplied, but there is no corresponding increase in temperature. Heat and temperature cannot therefore be the same thing. e three most common temperature scales are degree Celsius, kelvin and degree Fahrenheit. ey can be used to explain what is meant by an arbitrary scale. A typical Ethiopian daytime temperature is 24°C and a typical night time temperature is 12°C. Can we say that it is twice as hot in the daytime as it is during the night? e equivalent temperatures on the Kelvin scale are 297 K and 285 K. On the Fahrenheit scale they are 75°F and 54°F. Neither of these scales shows a 2 to 1 relationship, which would be the case if the scale was an absolute scale. Discuss with the students the dierence between heat and temperature at a particle level, emphasising that temperature is related to the average kinetic energy of the particles and does not depend on the number of particles present. Heat is a measure of the total energy, kinetic and potential, of all the particles within a substance. Remind students that when the water was heated, initially the kinetic energy of the particles increased, so the temperature rose. But what happened when the temperature reached 100°C? e potential energy increased and the bonds between particles were broken. To show how thermometers are calibrated, use a round-bottomed ask lled with coloured water. Fit a holed bung with a long tube. Some of the coloured water will rise up the tube. Place the ask in a large beaker of melting ice at 0C. Mark on the tube the position of the water level. Replace the melting ice with boiling water. e water in the ask expands up the long tube. Mark the new position at 100°C. Use a rule to divide the distance between the two marks into 100 equal divisions. Each gap represents 1°C. Use the thermometer you have made to measure room temperature. Compare with a laboratory thermometer. It should agree within a degree or two. Melting ice and boiling water are the two xed points on the Celsius scale. e thermometer works because of expansion; this will be examined in the next section. ermal images are oen used to show changes in temperature. ey are used by re and rescue services to locate people trapped in buildings or lost in open countryside. ere are many such images available to view from the internet. http://www.x20.org/ has a good gallery showing animals, intruders, energy loss from homes and vehicles. Grade 9 87 6OJU5FNQFSBUVSFBOEIFBU To illustrate thermal equilibrium, lag the walls of a cardboard box with foam. Leave just enough room inside the box to stand two cans touching side by side. Fill one can with melted ice and one with boiling water. Put a lagged lid on the box but have two small holes in the lid to allow thermometers to reach into the two cans. Record the temperatures every half-minute. Students can plot two graphs on the same axes; a warming curve for the cold water and a cooling curve for the hot. Both curves will tend towards a steady temperature. At this temperature, the two cans of water, and the thermometers, are in thermal equilibrium. Ask students why the kitchen gets cold when the door of the freezer is le open. Is it because all the cold comes out? Explain that energy ows from a warmer to a cooler body, so energy ows from the kitchen into the freezer. is ow of energy reduces the temperature in the kitchen. Explain, in simple terms, the laws of thermodynamics. SA = starter activity MA = main activity CA = concluding activity What are heat and temperature? SA *OTNBMMHSPVQTTUVEFOUTEJTDVTTXIBUUIFZVOEFSTUBOECZUIFUFSNTAIFBUBOEAU 5IFZGFFECBDLJEFBT MA *OTNBMMHSPVQTTUVEFOUTIFBUBCFBLFSPGXBUFSBOESFDPSEUIFUFNQFSBUVSFFWF NJOVUFTFFQBHFPGUIJTCPPL5IFZEJTDVTTUIFSFTVMUT CA "DUJWJUZ The laws of thermodynamics SA *OQBJSTTUVEFOUTEJTDVTTXIZBLJUDIFOHFUTDPMEXIFOBGSFF[FSEPPSJTMFGUPQFO GFFECBDLJEFBT MA 8PSLJOBTNBMMHSPVQUPQSPEVDFBQPTUFSBCPVUUIFMBXTPGUIFSNPEZOBNJDT CA 3FWJFXRVFTUJPOTUPCFUBDLMFEJOQBJST Activities t1SBDUJTFDPOWFSUJOHUFNQFSBUVSFTGSPNUIF$FMTJVTTDBMFUPUIF, from the Kelvin scale to Celsius. t4UVEFOUTDBONPEFMUIFCFIBWJPVSPGQBSUJDMFTBTUIFZBSFIFBUFE4U standing still in a regular pattern (0 K). Move from side to side, gradually increasing in speed and amount moved (solid being heated). Move around but keep in roughly the same total space (becoming a liquid). Move around faster (liquid being heated). Start to move around the whole room (changing into a gas). Resources http://physics.about.com/od/thermodynamics/a/lawthermo.htm Where next? Laboratory thermometers work because liquids expand when heated. e next section explains why things expand and compares the amounts by which solids, liquids and gases expand when they are heated. 88 Grade 9 6OJU5FNQFSBUVSFBOEIFBU Answers to review questions 1. e average kinetic energy of particles in iron at 500 K will be twice that at 250 K. 2. As particles vibrate they spread out more. 3. Energy ows from a hot body to a cold one until thermal equilibrium is reached; work needs to be done on the system to reverse the process. 4. a) 0 K b) 273.15 K c) 1273 K &YQBOTJPOPGTPMJETMJRVJETBOEHBTFT Learning Competencies 5IJTTFDUJPO TIPVME GJMMBQQSPYJNBUFMZ 3 periods of UFBDIJOHUJNF #ZUIFFOEPGUIJTTFDUJPOTUVEFOUTTIPVMECFBCMFUP t %FTDSJCFUIFUIFSNBMFYQBOTJPOPGTPMJETBOEEFSJWFUIFFYQSFTTJPOGPSUIF MJOFBSBOETVSGBDFFYQBOTJPOPGTPMJET t 'JOEUIFSFMBUJPOTIJQCFUXFFOUIFDPFGGJDJFOUTPGMJOFBSBSFBBOEWPMVNF FYQBOTJPOBOETPMWFSFMBUFEQSPCMFNT t ,OPXBQQMJDBUJPOTPGUIFUIFSNBMFYQBOTJPOPGNBUFSJBMT t %JTUJOHVJTICFUXFFOBQQBSFOUBOESFBMFYQBOTJPOPGBMJRVJEBOETPMWF QSPCMFNTJOWPMWJOHUIFFYQBOTJPOPGMJRVJET VTJOHV = V oT t &YQMBJOUIFBCOPSNBMFYQBOTJPOPGXBUFS t $PNQBSFUIFFYQBOTJPOPGHBTFTXJUIUIFFYQBOTJPOPGTPMJETBOEMJRVJET Starting off is section builds on the explanation of particle behaviour when substances are heated to examine expansion in one, two and three dimensions. e consequences of expansion are examined together with some useful applications. Teaching notes Begin by reminding students how particles behave when heated – they occupy a greater amount of space. It is dicult to see solids expand but it is possible to see the eect. Clamp one end of a copper rod rmly so that it cannot move and balance the other end of the rod on an upturned glass beaker. Between the rod and the beaker, place a short length of dowel with a pin stuck vertically in the dowel. Heat the copper rod; as it expands it will roll the dowel and the pin rotates to provide visible evidence of expansion. Introduce coecients of expansion and derive the expressions linking area () and volume () coecients to the linear () coecient. tàß táß Grade 9 89 6OJU5FNQFSBUVSFBOEIFBU Activity 7.2: Answer brass: Y -4N DPODSFUF N Activity 7.3: Answer N 2 Activity 7.4: Answer 3 N Activity 7.5: Answer N 3 It is important to understand some of the consequences of expansion, particularly as the forces involved in expansion and contraction can be very large. Fortunately, concrete and iron have very similar expansions. If they did not, it would not be possible to use iron when reinforcing concrete. If iron expanded more than concrete, concrete would crack when it got hot. e roadways that form the span of bridges are oen rested on rollers at each end of the bridge. If the roadway was not free to move, it would buckle in hot weather. Expansion gaps allow for this freedom to move, not only with roads but also railways. Modern railways use continuous welded rail in lengths of nearly 0.5 km. Where one length meets the next, there is a sliding overlap. is gives a smoother ride. is type of rail is replacing 20 m lengths that butt up to each other with a centimetre gap between. e expansion and contraction of metals can be used to advantage. As well as hot riveting, metal hoops are heated and dropped over barrels to pull the wood tight; the metal rims of wooden cart wheels do a similar job. Cars and bicycles have rubber tyres that t onto wheel rims. Train wheels also have tyres. ese are rims of steel about 2.5 cm thick, which are heated then shrunk onto the rest of the wheel. is means that when the rim wears out, the whole wheel does not need to be replaced. e wheels themselves can be shrunk onto the axles. e t is very tight. Ask students why the level of liquid in a thermometer drops when placed in a hot liquid before rising. Discuss the dierence between real and apparent expansion. Wheras it is dicult to see solids expanding, the thermometer shows that the expansion of liquids is considerably greater. You can show that gases expand even more by using an empty round-bottomed ask tted with a capillary tube through a rubber bung. Introduce a thread of coloured liquid into the capillary tube by inverting the end into the coloured liquid and warming the ask with your hands. e air expands and bubbles will be seen in the liquid. Only allow a few bubbles to escape before moving your hands to hold the ask by its neck. As the ask cools, a thread of liquid is drawn into the capillary tube. Remove the tube from the liquid and stand the ask upright. Cool the ask gently with water and the thread moves down towards the ask, warm the ask again with your hands and it moves up the tube. Only a small temperature dierence moves the thread by a signicant amount showing that gases expand more than liquids. Explain the anomalous expansion of water. is phenomenon explains how sh are able to survive in frozen ponds. e water at the bottom of the pond is at 4°C even though the top of the pond is frozen. 90 Grade 9 6OJU5FNQFSBUVSFBOEIFBU SA = starter activity MA = main activity CA = concluding activity The expansion of solids SA %FNPOTUSBUFUIFIPPQBOECBMMFYQFSJNFOUQBHFPG4UVEFOUTh#PPL4UVEFOUTU PCTFSWBUJPOTJOTNBMMHSPVQTBOEXPSLPOBOFYQMBOBUJPO'FFECBDLJEFBT MA "DUJWJUZ "DUJWJUZ "DUJWJUZ CA 8JUIBQBSUOFSEJTDVTTUIFRVFTUJPOA8IZEPZPVUIJOLUIBUJUJTTBGFUPCVJMEBCSJE PVUPGDPODSFUFSFJOGPSDFEXJUIJSPO 'FFECBDLJEFBT Applications of thermal expansion SA 8JUIBQBSUOFSEJTDVTTUIFRVFTUJPOA)PXDPVMEZPVUFMMUIBUUIFQIPUPPGUIFFYQB KPJOUPOBCSJEHFXBTUBLFOPOBDPMEEBZ TFF4UVEFOUTh#PPLQBHF'FFECBDLJEFBT MA *OTNBMMHSPVQTTUVEFOUTDBMJCSBUFBUIFSNPNFUFSTFFQBHFPGUIJTCPPL CA 3FWJFXRVFTUJPOT¦UPCFUBDLMFEJOQBJST Expansion of liquids and gases SA 8JUIBQBSUOFSTUVEFOUTEJTDVTTXIBUUIFZUIJOLXJMMIBQQFOUPUIFMJRVJEJO'JHVS UIF4UVEFOUTh#PPLBOEGFFECBDLJEFBT MA 4UVEFOUTDBSSZPVUFYQFSJNFOUJO'JHVSFJOTNBMMHSPVQT "DUJWJUZ CA 3FWJFXRVFTUJPOT¦UPCFUBDLMFEJOQBJST Activities t1SBDUJTFDBMDVMBUJPOTVTJOHDPFDJFOUTPGFYQBOTJPO t4IPXUIBUBDNHBQJTBMBSHFFOPVHIHBQCFUXFFONMFOHUITPGJSPOSBJMJG temperatures vary from <10°C to 30°C. Resources http://www.project2061.org/publications/2061connections/2007/media/KS1docs/ abell_deboer_roseman_poster.pdf Where next? e next section looks at how much energy is transferred when the temperature of an object changes or when it changes state from solid to liquid or liquid to gas. Answers to review questions 1. particles vibrate over larger distances 2. 5.7 mm 3. 0.6714 m2 2T 2); 4. Ahl h2; l c2 (1 + 2T + 2T 2); lh l c + l cT; AhA c (1 + 2 T + 2 2 2 2 lh l c + l cT) ; but T is approx zero; 2 2 ; M c (1 + T) AhA c (1 + 2Tàß Grade 9 91 6OJU5FNQFSBUVSFBOEIFBU 3 5. 0.00147 m 6. liquid is in container; container expands as well; real expansion is greater than apparent expansion 7. molecules move closer together as water cools; at 4°C start to form second hydrogen bond; further apart to allow hydrogen bond to form 5IJTTFDUJPO TIPVME 2VBOUJUZPGIFBUTQFDJGJDIFBUDBQBDJUZBOEIFBUDBQB GJMMBQQSPYJNBUFMZ 3 periods of Learning Competencies UFBDIJOHUJNF #ZUIFFOEPGUIJTTFDUJPOTUVEFOUTTIPVMECFBCMFUP t %FTDSJCFUIFGBDUPSTUIBUBGGFDUUIFBNPVOUPGIFBUBCTPSCFEPSM CZBCPEZ t %FGJOFUIFUFSNTTQFDJGJDIFBUDBQBDJUZBOEIFBUDBQBDJUZBOEDB UIFBNPVOUPGIFBUFOFSHZBCTPSCFEPSMJCFSBUFECZBCPEZVTJOH Q = mc∆T t $BMDVMBUFUIFIFBUDBQBDJUZPGBCPEZ t *EFOUJGZEJGGFSFOUVOJUTPGIFBUFOFSHZ t &YQMBJOUIFTJHOJGJDBODFPGUIFIJHITQFDJGJDIFBUDBQBDJUZPGXBU t 6TFUIFSFMBUJPOTIJQIFBUMPTUIFBUHBJOFEUPTPMWFQSPCMFNTJOWP IFBUFYDIBOHF t %FTDSJCFUIFVTFTPGBDBMPSJNFUFS Starting off is section builds on the use of heat as a form of energy to change the temperature of a material. It introduces the term specic heat capacity and examines why it is advantageous to have a high value for specic heat capacity. Activity 7.6: Answer Teaching notes TID+LH, Begin by asking students to perform a thought experiment. Show them a 250 ml beaker of water and tell them it takes 1 minute with an electrical heater to raise the temperature by 1°C. Ask them how long it will take to raise the temperature by 2°C. ey should say 2 minutes. Now show them a 500 ml beaker of water and ask how long it will take to raise the temperature by 1°C using the same heater. Again, it should take 2 minutes. Tell them that no energy is lost to the surroundings. is will allow them to appreciate that energy supplied is directly related to both mass being heated and temperature rise. Finally, show them a 250 g block of copper. Tell them it is the same mass as the water in the 250 ml beaker. Ask how long it will take to raise the temperature by 1°C. ey should not be able to answer as it is a dierent material. is leads on to the idea that dierent materials have a property that is related to the material itself – the specic heat capacity. Q+ Activity 7.7: Answer TIDMJRVJE +LH, Activity 7.8: Answer ID+,UIF NBTTPGUIFCBMM Dene the term specic heat capacity and derive the expression Q = mcT. 92 Grade 9 6OJU5FNQFSBUVSFBOEIFBU Demonstrate how to calculate the specic heat capacity of both a solid and a MJRVJEVTJOHUIFQSJODJQMFPGIFBUHBJOFECZDPPMFSCPEZIFBUMPTUCZXBSNFS body. is can be done either by using an electrical heater to supply the energy or using the method of mixtures. Whichever method is used, the equipment does need to be well lagged to prevent energy loss to the surroundings. e method of mixtures requires a quick transfer of the hot block into the cold water and care taken to record the maximum temperature reached on the thermometer, not the temperature immediately aer transfer. Introduce the term heat capacity and note that the dierence between this and specic heat capacity is the lack of reference to mass. e word specic means related to unit mass. Discuss the advantages from water having a very high specic heat capacity. It stores energy eectively for use in domestic hot water systems and central heating systems and is an eective coolant in engines. SA = starter activity MA = main activity CA = concluding activity What is meant by the term specific heat capacity? SA 4UVEFOUTXPSLJOQBJSTUPEJTDVTTGBDUPSTBGGFDUJOHUIFBNPVOUPGIFBUSFRVJ UFNQFSBUVSFPGBTVCTUBODF'FFECBDLJEFBT MA "DUJWJUZ CA 4UVEFOUT XPSLJOQBJST UPQSPEVDF B QPTUFS TIPXJOHUIFTUFQT SFRVJSFE JOB TQFDJGJD IFBUDBMDVMBUJPO Finding the specific heat capacity of a substance SA 4UVEFOUTXPSLXJUIBQBSUOFSUPNBLFBTVNNBSZPG4UVEFOUTh#PPLQBHFT¦ MA "DUJWJUZ 4UVEFOUTXPSLJOTNBMMHSPVQTUPGJOEUIFTQFDJGJDIFBUDBQBDJUZPGBCPMUVTJ PGNJYUVSFT CA 4UVEFOUTXSJUFBSFQPSUPOUIFNBJOBDUJWJUZ What is the heat capacity of a body? SA *OQBJSTTUVEFOUTEJTDVTTUIFRVFTUJPOA)PXEPFTUIFIJHITQFDJGJDIFBUDBQBDJUZ NBLFJUTPVTFGVMBTBDPPMBOU 'FFECBDLJEFBT MA "DUJWJUZ CA 3FWJFXRVFTUJPOTUPCFUBDLMFEJOQBJST Activities t1SBDUJTFDBMDVMBUJPOTJOWPMWJOHIFBUDBQBDJUZBOETQFDJDIFBUDBQBDJUZ t%JTDVTTXIZJUJTJNQPSUBOUUPMBHDBMPSJNFUFSTJOIFBUFYDIBOHFFYQFSJNFOUT and transfer solids and liquids quickly in method of mixtures experiments. t4VHHFTUPUIFSFYBNQMFTXIFSFJUJTCFOFDJBMUPIBWFBIJHITQFDJDIFBU capacity. Resources http//www.ausetute.come.au/heatcapa.html Grade 9 93 6OJU5FNQFSBUVSFBOEIFBU Where next? e next section looks at energy transferred when materials change state when heated or cooled. Experimentally, when nding values for specic latent heat, a change in temperature is usually involved. is will need the experience gained from the previous section to be applied. Answers to review questions 1. e amount of energy required to change the temperature of 1 kg of water by 1 K. 2. 2700 J 3. 910 J/kg K 4. 2520 J 5IJTTFDUJPO TIPVME $IBOHFTPGTUBUF GJMMBQQSPYJNBUFMZ 4 periods of Learning Competencies UFBDIJOHUJNF #ZUIFFOEPGUIJTTFDUJPOTUVEFOUTTIPVMECFBCMFUP t %FGJOFUIFUFSNTMBUFOUIFBUMBUFOUIFBUPGGVTJPOBOEMBUFOUIFB WBQPSJTBUJPO t 4PMWFQSPCMFNTJOWPMWJOHDIBOHFPGTUBUF Starting off is section builds on the knowledge that heating an object does not always raise its temperature. Energy is required, or released, whenever a change of state occurs Activity 7.9: Answer Teaching notes Begin by heating a block of ice at a temperature below zero until it has changed into water, then increased in temperature until it boils and most has evaporated. It is important to heat gently but with a constant energy source. Record the temperature every 15 s. Students can plot the heating curve. e specic heat capacity of ice is only 2100 J/kg K so ask students to think about the gradient of the graph when the ice is being heated compared to when the water is being heated. Activity 7.10: Answer 2 090-+ 2 + Explain the meaning of latent as hidden. e heat is not raising the temperature, so its eect is hidden from the measuring instrument although visible to us as ice melts or water turns into vapour. Explain the dierence between specic latent heat of fusion and specic latent heat of vaporisation; emphasise the fact that it requires more energy to completely separate particles when a liquid changes into a gas than it does when a solid changes to a liquid and the particles are still bonded together. e specic latent heat can be found in a similar way to specic heat capacity CZUIFNFUIPEPGNJYUVSFTBOEVTJOHUIFQSJODJQMFUIBUIFBUHBJOFEIFBU In this case, when nding specic latent heat of fusion, the heat is gained by the solid warming, the solid changing to a liquid and the liquid warming. If nding 94 Grade 9 6OJU5FNQFSBUVSFBOEIFBU the specic latent heat of evaporation, the heat lost is by the gas cooling, the gas condensing and the liquid cooling. Show students how to nd the specic latent heat of fusion of ice. e specic latent heat of evaporation can be found by bubbling steam through water. e steam from a steam generator can be assumed to be at 100°C so this simplies the calculation by not having to consider the cooling of the water vapour. SA = starter activity MA = main activity CA = concluding activity Heating and cooling curves SA *OTNBMMHSPVQTTUVEFOUTQMPUUIFIFBUJOHDVSWFGPSBCMPDLPGJDFVOUJMJUDI MA 4UVEFOUTXPSLJOTNBMMHSPVQTUPFYQMPSFXIBUIBQQFOTUPBRVBOUJUZPGXBUFS BNPVOUTPGTBMUBEEFEBTJUDPPMTBOEQMPUBDPPMJOHDVSWF CA 4UVEFOUTXPSLXJUIBQBSUOFSUPTVNNBSJTF4UVEFOUTh#PPLQBHFT¦ Specific latent heat (1) SA *OQBJSTTUVEFOUTEJTDVTTXIBUUIFZVOEFSTUBOECZUIFUFSNAMBUFOU'FFECBDLJEF MA &YBNQMFTPGDBMDVMBUJPOPGTQFDJGJDMBUFOUIFBUUPCFUBDLMFEJOQBJST CA 3FWJFXBOTXFSTUPQSPCMFNTJONBJOBDUJWJUZ Specific latent heat (2) SA *OQBJSTEJTDVTTXIZJUUBLFTNPSFFOFSHZUPDPNQMFUFMZTFQBSBUFQBSUJDMFTX DIBOHFTJOUPBHBTUIBOJUEPFTXIFOBTPMJEDIBOHFTJOUPBMJRVJE'FFECBDLJEFBT MA "DUJWJUZ CA 3FWJFXRVFTUJPOTUPCFUBDLMFEJOQBJST The specific latent heat of fusion of ice SA *OQBJSTTUVEFOUTEJTDVTTXIBUJTIBQQFOJOHBUBNPMFDVMBSMFWFMBTJDFNFMUT'FF MA 4UVEFOUTXPSLJOTNBMMHSPVQTUPEFUFSNJOFUIFTQFDJGJDMBUFOUIFBUPGGVTJP CA &OEPGVOJURVFTUJPOTUPCFUBDLMFEJOQBJST Activities t6TFHJWFOEBUBUPQMPUIFBUJOHDVSWFGPSJDFVOUJMJUJTDIBOHFEUPXBUFSWBQPVS t1SBDUJTFDBMDVMBUJPOTJOWPMWJOHTQFDJDMBUFOUIFBU Resources http://zonalandeducation.com/mstm/physics/mechanics/energy/ heatandtemperature/changesofphase/changeofstate.html Answers to review questions 1. 2090 J 2. 76 440 J 3. 18 375 J 4. e amount of energy required to change the state of 1 kg of magnesium from solid to liquid at its melting point. 5. 298 200 J Grade 9 95 6OJU5FNQFSBUVSFBOEIFBU Answers to end of unit questions 1. temperature – arbitrary scale; related to average kinetic energy of particles heat – absolute scale; related to total energy, kinetic and potential, of particles 2. energy transferred from hot body to cold (2nd law); no energy gain or loss in system (1st law); two bodies reach thermal equilibrium 3. 30.00825 m –6 m3; apparent expansion less because container expands as well 4. 3.75 × 10 5. 117.6 J/kg/K 6. a) 300 J/K b) 400 J/kg/K 7. 39 4C 8. 28 462 000 J 9. 10.344 148 J/kg 96 Grade 9 Wave motion and sound Learning Competencies for Unit 8 By the end of this unit students should be able to: t %FGJOFUIFUFSNTXBWFBOEXBWFQVMTF Unit 8 This unit should GJMMBQQSPYJNBUFMZ 16 periods of UFBDIJOHUJNF t %FTDSJCFMPOHJUVEJOBMBOEUSBOTWFSTFXBWFT t %FGJOFUIFUFSNTDPNQSFTTJPOBOESBSFGBDUJPO t %FGJOFBOEJEFOUJGZUIFGPMMPXJOHGFBUVSFTPGBXBWFDSFTUUSPVHI XBWFMFOHUIGSFRVFODZBNQMJUVEFBOEUJNFQFSJPE t %JTUJOHVJTICFUXFFONFDIBOJDBMXBWFTBOEFMFDUSPNBHOFUJDXBWFT t *EFOUJGZUSBOTWFSTFBOEMPOHJUVEJOBMXBWFTJOBNFDIBOJDBMNFEJB t 4UBUFUIFXBWFFRVBUJPOBOEVTFJUUPTPMWFQSPCMFNT t %FTDSJCFUIFDIBSBDUFSJTUJDQSPQFSUJFTPGXBWFTJODMVEJOHSFGMFDUJPO SFGSBDUJPOEJGGSBDUJPOBOEJOUFSGFSFODF t %FGJOFUIFUFSNTEJGGSBDUJPOBOEJOUFSGFSFODF t *EFOUJGZTPVOEXBWFTBTMPOHJUVEJOBMNFDIBOJDBMXBWFTBOEEFTDSJCFIPX UIFZBSFQSPEVDFEBOEIPXUIFZQSPQBHBUF t $PNQBSFUIFTQFFEPGTPVOEJOEJGGFSFOUNBUFSJBMTBOEEFUFSNJOFUIF TQFFEPGTPVOEJOBJSBUBHJWFOUFNQFSBUVSF t %FGJOFUIFJOUFOTJUZPGBTPVOEXBWFBOETPMWFQSPCMFNTVTJOHUIF JOUFOTJUZGPSNVMB t &YQMBJOUIFNFBOJOHPGUIFUFSNTFDIPSFWFSCFSBUJPOQJUDIMPVEOFTTBOE RVBMJUZ t &YQMBJOUIFSFGMFDUJPOBOESFGSBDUJPOPGTPVOEBOEEFTDSJCFTPNF BQQMJDBUJPOT 8BWFQSPQBHBUJPO Learning Competencies 5IJTTFDUJPO TIPVME GJMMBQQSPYJNBUFMZ 2 periods of UFBDIJOHUJNF #ZUIFFOEPGUIJTTFDUJPOTUVEFOUTTIPVMECFBCMFUP t %FGJOFUIFUFSNTXBWFBOEXBWFQVMTF t %FTDSJCFMPOHJUVEJOBMBOEUSBOTWFSTFXBWFT t %FGJOFUIFUFSNTDPNQSFTTJPOBOESBSFGBDUJPO Grade 9 97 6OJU8BWFNPUJPOBOETPVOE Starting off is topic deals with the transfer of energy by waves. Light waves, sound waves, microwaves, radio waves are all familiar to us as energy carriers. e important fact about a wave is that it transfers energy from one place to another without itself moving between the two places. Teaching notes It is worth spending a short time discussing the idea of wave motion. Ask a group of students to line up and perform a Mexican wave. As they move up and down, the wave moves from one end to the other. A Mexican wave is an example of a transverse wave. Activity 8.1: Answer 4UVEFOUThPXO results Activity 8.2: Answer 4UVEFOUThPXO results Activity 8.3: Answer 4UVEFOUThPXO results Activity 8.4: Answer 4UVEFOUThPXO results 98 Place a toy duck in a large trough of water, midway between the centre and the edge. Drop a small piece of Plasticine into the middle of the trough. A wave pulse moves to the edge of the trough. Does the duck also move? Drop several pieces of Plasticine at 1 s intervals. A continuous wave now moves to the edge of the trough. e duck still bobs up and down and does not move to the edge. Water waves are transverse. Use a rubber tube, length of rope or a slinky spring to show the dierence between a wave pulse and a continuous wave. Emphasise that in a transverse wave, the direction of displacement (or vibration) is at right angles to the direction in which the wave moves. Identify the crest and trough of the wave. Provide examples of transverse waves to include. tXBUFS tMJHIU tNJDSPXBWFT tSBEJPXBWFT t9SBZT tWJCSBUJOHTUSJOHT t4XBWFTJOFBSUIRVBLFT 4UVEFOUTDBOBMTPTJNVMBUFBMPOHJUVEJOBMXBWFFZTIPVMETUBOEJO shoulder to shoulder with their arms linked. e student at the end moves from TJEFUPTJEF"XBWFQVMTFNPWFTBMPOHUIFMJOF*GUIFTJEFUPTJEFNPUJPO repeated, a continuous wave travels from one end of the line to the other. e important points to note are that at any instant, some students may be in their normal position, some may be to the le and some to the right, they may be moving in opposite directions. 6TFBTUSFUDIFEPVUTMJOLZTQSJOHUPSFJOGPSDFUIJTNPUJPO4FOEBQVM TQSJOHBOEUIFOBDPOUJOVPVTXBWF4PVOEJTBMPOHJUVEJOBMXBWFBOE spring can be thought of as representing layers of air between the sound source BOEUIFSFDFJWFS*UDBOCFRVJUFFFDUJWFUPTQFBLJOUPPOFFOEPGUIFTQ ear at the other end and in slow motion demonstrate the vibration of air layers along the length of the spring. Emphasise that in a longitudinal wave, the direction of displacement (or vibration) is parallel to the direction in which the wave moves. Identify the areas of compression and rarefaction of the wave. Grade 9 6OJU8BWFNPUJPOBOETPVOE 4PVOEJTBWJCSBUJPO4USJLFBUVOJOHGPSLBOEMJTUFOoJUDBOOPUCFIFBSE1MBDFUIF stem of the fork onto a table and the sound can be heard; the whole table starts to vibrate, but only by a very small amount. is causes a greater volume of air to WJCSBUF4VTQFOEBUBCMFUFOOJTCBMMGSPNBMFOHUIPGDPUUPO5PVDIUIFWJCSBUJOH fork gently against the ball. Although the vibration is too small to be visible with UIFOBLFEFZFUIFFFDUPOUIFUBCMFUFOOJTCBMMJTRVJUFESBNBUJD:PVDBOGFFMUIF vibration from a large loudspeaker. Provide examples of longitudinal waves to include: tTPVOE tVMUSBTPVOE t1XBWFTJOFBSUIRVBLFT tTIPDLXBWFGSPNFYQMPTJPO SA = starter activity MA = main activity CA = concluding activity What are waves? SA *OBTNBMMHSPVQTUVEFOUTQFSGPSNB.FYJDBOXBWF MA "DUJWJUZ CA 4UVEFOUTXPSLXJUIBQBSUOFSUPTVNNBSJTFQBHFT¦PG4UVEFOUTh#PPL Longitudinal and transverse waves SA *OTNBMMHSPVQTTUVEFOUTFYQMPSFFYBNQMFTPGUSBOTWFSTFXBWFTTFFQBHFPG MA CA "DUJWJUZ "DUJWJUZ "DUJWJUZ 3FWJFXRVFTUJPOTUPCFUBDLMFEJOQBJST Activities t6TFBMFOHUIPGSVCCFSUVCJOHPSSPQFUPQSPEVDFUSBOTWFSTFXBWFT t6TFBTMJOLZTQSJOHUPQSPEVDFMPOHJUVEJOBMXBWFT t%SBXQJDUVSFTUPSFQSFTFOUIPXUSBOTWFSTFBOEMPOHJUVEJOBMXBWFTBQQFBSUP change with time. Resources http://paws.kettering.edu/~drussell/Demos/Waves/wavemotion.html Where next? Waves can be either mechanical or electromagnetic. All waves have certain DIBSBDUFSJTUJDTBNQMJUVEFXBWFMFOHUIGSFRVFODZTQFFEBOEQFSJPEXIJDINVTU be identied to allow the wave to be fully described. Grade 9 99 6OJU8BWFNPUJPOBOETPVOE Answers to review questions DPOUJOVPVToSFQFBUFEWJCSBUJPOUIBUUSBOTGFSTFOFSHZDPOUJOVB QMBDFUPBOPUIFSQVMTFoTJOHMFEJTQMBDFNFOUUIBUUSBOTGFSTFO place to another 2. particles vibrate about a rest position 3. particle vibration at right angles to wave direction; water, light, radio, NJDSPXBWF4XBWF9SBZJOGSBSFEVMUSBWJPMFU QBSUJDMFWJCSBUJPOQBSBMMFMUPXBWFEJSFDUJPOTPVOEVMUSBTPV wave 5IJTTFDUJPO TIPVME .FDIBOJDBMXBWFT GJMMBQQSPYJNBUFMZ 5 periods of Learning Competencies UFBDIJOHUJNF #ZUIFFOEPGUIJTTFDUJPOTUVEFOUTTIPVMECFBCMFUP t %FGJOFBOEJEFOUJGZUIFGPMMPXJOHGFBUVSFTPGBXBWFDSFTUUSPV XBWFMFOHUIGSFRVFODZBNQMJUVEFBOEUJNFQFSJPE t %JTUJOHVJTICFUXFFONFDIBOJDBMXBWFTBOEFMFDUSPNBHOFUJDXBW t *EFOUJGZUSBOTWFSTFBOEMPOHJUVEJOBMXBWFTJOBNFDIBOJDBMNF Starting off is section builds on the descriptions of transverse and longitudinal waves by JEFOUJGZJOHUIFJSDIBSBDUFSJTUJDTJODMVEJOHBNQMJUVEFXBWFMFO period and speed, as well as the more fundamental characteristic of whether they are mechanical waves or electromagnetic. Activity 8.5: Answer Teaching notes BT CT DT Begin by asking the students to once again produce a Mexican wave. Identify each characteristic of the wave by priming the students to behave in a certain way. t"NQMJUVEFoDIBOHFUIFBNPVOUCZXIJDIUIFTUVEFOUTSBJTFUIFJSIBOET JOUIFBJS4IPXEJFSFOUBNQMJUVEFTBOEJEFOUJGZBHJWFOBNQMJUVEF NBYJNVNEJTQMBDFNFOUGSPNUIFFRVJMJCSJVNQPTJUJPO&YQMBJOUI BEJTQMBDFNFOUBCPWFUIFFRVJMJCSJVNQPTJUJPOBOEBUSPVHIJTBE CFMPXUIFFRVJMJCSJVNQPTJUJPO t4QFFEoDIBOHFUIFUJNFJUUBLFTGPSUIFOFYUQFSTPOUPSFTQPOEFTQFF the wave is the length of the line of students divided by the time it takes for the wave to travel from one end to the other. Ask students to measure several wave speeds. t8BWFMFOHUIoGSFF[FUIFBDUJPOBOETIPXUIFNFBOJOHPGXBWFMFOHUI" common misconception is to measure wavelength along the axis from one QPJOUPG[FSPEJTQMBDFNFOUUPUIFOFYUJTJTJOGBDUIBMGBXBWFMFO B)[ C)[ D)[ Activity 8.6: Answer 4UVEFOUThPXO results 100 Grade 9 6OJU8BWFNPUJPOBOETPVOE t'SFRVFODZoDPVOUUIFOVNCFSPGXBWFTQBTTJOHBQPJOUFBDITFDPOE4IPX UIBUBTUIFGSFRVFODZJODSFBTFTUIFXBWFMFOHUIEFDSFBTFT t1FSJPEoUIFUJNFJUUBLFTGPSPOFDPNQMFUFXBWFUPQBTTBQPJOU"TLPOF group of students to measure the period and another group to measure the GSFRVFODZ4IPXUIBUGSFRVFODZQFSJPE 6TFUIFTUVEFOUTUPQSPEVDFBMPOHJUVEJOBMXBWF'SFF[FUIFBDUJPOUPTIPXB wavelength. All of the other characteristics are the same but more dicult to show on a diagram. Discuss the dierence between mechanical waves (vibrate through a medium) and FMFDUSPNBHOFUJDXBWFTEPOPUSFRVJSFBNFEJVN3FNJOETUVEFOUTPGUIFXBWFT already discussed and class them appropriately. Introduce the remainder of the electromagnetic spectrum and illustrate how electromagnetic waves progress via electric and magnetic elds vibrating at right angles to one another and at right angles to the wave direction. -PPLBUUIFSBOHFPGGSFRVFODJFTBOEXBWFMFOHUITJOUIFFMFDUSPNBHOFUJDTQFDUSVN BOEFNQIBTJTFUIBUBMMTVDIXBWFTUSBWFMBUUIFTBNFTQFFEoUIFWFMPDJUZPGMJHIU oNT*GBQQSPQSJBUFJOUSPEVDFUIFQPXFSTPGXSJUUFOBT x or x together with the prex names. e science convention is that x increases in multiples of 3. is means that the prexes centi (as in centimetre) and deci (as JOEFDJMJUSFBSFOPUQSFGFSSFEVOJUTBMUIPVHIBSFTUJMMRVJUFXJEFMZVTFE"TXBWFT are energy carriers, it is worth mentioning that the shorter the wavelength (higher UIFGSFRVFODZPGFMFDUSPNBHOFUJDSBEJBUJPOUIFNPSFFOFSHZJTUSBOTGFSSFE Examine the waves in the electromagnetic spectrum and their uses. Evidence for UIFJODSFBTJOHFOFSHZPGUIFXBWFTBTUIFJSGSFRVFODZJODSFBTFTDBOCFTFFOCZ comparing the 'damage' done to the skin by radio waves (none), ultraviolet (sun tan leading to sunburn or skin cancer) and gamma (destroys cells inside the body oUSFBUTDBODFS Water waves are probably the most familiar waves. ey can be examined with the aid of a ripple tank or any other water trough. Emphasise that the speed of waves depends on the depth of water. e waves travel slower in shallower water but UIFJSGSFRVFODZJODSFBTFTBTUIFJSXBWFMFOHUIEFDSFBTFTFBNQMJUVEFPGUIFXBWF also increases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rade 9 101 6OJU8BWFNPUJPOBOETPVOE SA = starter activity MA = main activity CA = concluding activity Waves characteristics (1) SA 8PSLJOHXJUIBQBSUOFSTUVEFOUTEJTDVTTXIBUUIFZVOEFSTUBOECZUFSNTBNQMJUVE BOEXBWFMFOHUI'FFECBDLJEFBT MA *OQBJSTTUVEFOUTQSPEVDFBQPTUFSUPTVNNBSJTF4UVEFOUTh#PPLQBHFT¦ CA 3FWJFXRVFTUJPOT¦UPCFUBDLMFEJOQBJST Waves characteristics (2) SA 4UVEFOUTQFSGPSNB.FYJDBOXBWFJOTNBMMHSPVQTCVUUIJTUJNFUIFZJEFOUJGZFBD DIBSBDUFSJTUJDPGUIFXBWFBTEFTDSJCFEPOQBHFPGUIJTCPPL MA "DUJWJUZ 4UVEFOUTXPSLJOQBJSTUPBEEUPUIFJSQPTUFSGSPNMBTUMFTTPOUPJODMVEFGSFRV QFSJPE CA 3FWJFXRVFTUJPOT¦UPCFUBDLMFEXJUIBQBSUOFS Electromagnetic spectrum SA *OTNBMMHSPVQTTUVEFOUTEJTDVTTUIFEJGGFSFODFTCFUXFFONFDIBOJDBMXBWFTB FMFDUSPNBHOFUJDXBWFT5IFZDMBTTUIFXBWFTUIFZIBWFBMSFBEZNFUBQQSPQSJBUF MA "DUJWJUZ CA 3FWJFXRVFTUJPOUPCFUBDLMFEXJUIBQBSUOFS Water waves SA 4UVEFOUTXPSLJOTNBMMHSPVQTUPMJTUBTNBOZFYBNQMFTBTQPTTJCMFPGXBUFSXB NFFUJOFWFSZEBZMJGF MA *OTNBMMHSPVQTTUVEFOUTJOWFTUJHBUFUIFCFIBWJPVSPGXBUFSXBWFTVTJOHBSJQ CA 4UVEFOUTXSJUFBSFQPSUPOUIFJOWFTUJHBUJPO Seismic waves SA 4UVEFOUTUBMLUPQBSUOFSBCPVUXIBUUIFZLOPXBCPVUFBSUIRVBLFTBOEGFFECBDLJ MA 4UVEFOUTXPSLXJUIBQBSUOFSUPNBLFBQPTUFSUPTVNNBSJTFQBHFT¦PGUIF4UVEFOU #PPL CA 3FWJFXRVFTUJPOUPCFUBDLMFEXJUIBQBSUOFS Activities t%SBXBEJBHSBNPGBUSBOTWFSTFXBWFBOEMBCFMBNQMJUVEFXBWFM trough. t1SBDUJTFDBMDVMBUJPOTPGXBWFTQFFEGSFRVFODZXBWFMFOHUIBOE t%SBXBEJBHSBNPGBMPOHJUVEJOBMXBWFBOEMBCFMUIFXBWFMFOHUI amplitude. t*OWFTUJHBUFUIFFMFDUSPNBHOFUJDNBHOFUJDTQFDUSVN'JOEPVUIPX the spectrum is produced and its uses. Resources http://www.glencoe.com/sec/science/voyages/voyagesgreen/unit1/Chapter2/ worksheets.shtml 102 Grade 9 6OJU8BWFNPUJPOBOETPVOE Where next? e next section looks at some of the properties of waves including reection, SFGSBDUJPOEJSBDUJPOBOEJOUFSGFSFODFFXBWFFRVBUJPOJTFYQMBJOFEJOUFSNTPG UIFGSFRVFODZBOEXBWFMFOHUIPGUIFXBWF Answers to review questions "NQMJUVEFJTUIFNBYJNVNEJTQMBDFNFOUGSPNFRVJMJCSJVNQPTJUJPO wavelength is the distance between two points of identical displacement on UXPBEKBDFOUXBWFTGSFRVFODZJTUIFOVNCFSPGDPNQMFUFXBWFTQBTTJOHB point in one second; period is the time taken for one complete wave to pass a point 2. A distance should be four times distance A BNQMJUVEFoDNXBWFMFOHUIoDN BNQMJUVEFoDNQFSJPEoT TNT )[ 7. Magnetic and electric elds vibrating at right angles to one another and at right angles to the wave direction. CPUITFJTNJDXBWFTCPUIUSBWFMUISPVHITPMJETPOMZQUSBWFMTUISPVHIMJRVJET 1MPOHJUVEJOBM4USBOTWFSTF1USBWFMTGBTUFSUIBO4 1SPQFSUJFTPGXBWFT Learning Competencies 5IJTTFDUJPO TIPVME GJMMBQQSPYJNBUFMZ 4 periods of UFBDIJOHUJNF #ZUIFFOEPGUIJTTFDUJPOTUVEFOUTTIPVMECFBCMFUP t 4UBUFUIFXBWFFRVBUJPOBOEVTFJUUPTPMWFQSPCMFNT t %FTDSJCFUIFDIBSBDUFSJTUJDQSPQFSUJFTPGXBWFTJODMVEJOHSFGMFDUJPO SFGSBDUJPOEJGGSBDUJPOBOEJOUFSGFSFODF t %FGJOFUIFUFSNTEJGGSBDUJPOBOEJOUFSGFSFODF Starting off JTTFDUJPOCVJMETPOUIFLOPXMFEHFPGGSFRVFODZBOEXBWFMFOHUIUPPCUBJO an expression for the speed of a wave. All waves show properties of reection, Grade 9 103 6OJU8BWFNPUJPOBOETPVOE refraction, diraction and interference. An understanding of these properties is FTTFOUJBMJOFYQMBJOJOHNVDIPGUPEBZTDPNNVOJDBUJPOUFDIOPMPHZ Activity 8.7: Answer Teaching notes TQFFEoNT QFSJPEoT #FHJOCZSFNJOEJOHTUVEFOUTXIBUJTNFBOUCZXBWFTQFFEGSFRVFODZB XBWFMFOHUI4IPXUIFNIPXUPPCUBJOUIFFRVBUJPO v = f and explain the dierence between how most expressions are obtained by a thorough mathematical derivation and how this is obtained by logic. GSFRo)[ QFSJPEoT GSFRo)[ XBWFMFOHUIoN Activity 8.8: Answer 4UVEFOUThPXO results 4UVEFOUTDBOTIPXSFFDUJPOPG light by using mirrors and a light source. Place a at mirror upright POBTIFFUPGQBQFS4IJOFUIFMJHIU onto the mirror. It is best if the front of the light source is covered with paper containing a narrow slit. e students can mark the path of the light as it travels to the mirror and is reected back again. e normal is a line drawn at right angles to the mirror at the point where the ray strikes the mirror. ey can measure the angles of incidence and reection to show UIFZBSFFRVBM Mirror Incident wave Angle of incidence Normal Angle of reflection Reflected wave e reection of sound can be shown using a sound source at one end of a tube pointed at a solid reecting surface. Listen to the reected sound using another tube pointed at the reecting surface. Adjust the position of this tube until the sound is loudest. Measurement of the reected sound could be made with a microphone connected to an oscilloscope or a sound level meter. Again, look at the relationship between the angle of incident sound and the angle of reected sound. 4UVEFOUTDBOTIPXUIFSFGSBDUJPOPGMJHIUCZQMPUUJOHUIF Light ray path of light as it passes through a glass block. ey can use the same light source as previously. Light changes direction as it passes from one material into another. It is deviated towards the normal when entering a denser material and away from the normal when entering a less dense material. ere is a relationship between the angles of incidence and refraction but it is CFZPOEXIBUJTSFRVJSFEBUUIJTUJNF Air Glass Air Light is refracted because it slows down when entering a denser material. Ask students to imagine an army marching along in very straight rows. ey come to some boggy ground. e rst soldiers to enter the boggy ground slow down but the others carry on marching at the same speed. Eventually, as they all reach the boggy ground, they are all marching slower. e row has changed direction, the speed has EFDSFBTFE F GSFRVFODZ SFNBJOT UIFTBNFUIFSFBSF TUJMM UIFTBNFOVNCFS PGSPXT passing a point every second) so the wavelength must decrease. is represents what happens to a light wave as it enters the glass block at an angle. 104 Grade 9 6OJU8BWFNPUJPOBOETPVOE It is not only waves that can be reected and refracted. Billiard balls, for example, obey the laws of reection when they rebound PUIFDVTIJPO)PXFWFSEJSBDUJPOBOEJOUFSGFSFODFBSF properties peculiar to waves. 4PVOEEJSBDUTWFSZFBTJMZFEJSBDUJPOPGTPVOEFYQMBJOTXIZ you can hear someone who is out of sight the other side of an open doorway or why you can hear trac noise round the corner of a building. Water waves diract when they pass through a gap. is can be demonstrated using a trough of water. FXBUFSOFFETUPCFGBJSMZTIBMMPXOPNPSFUIBUDNEFFQ4USBJHIUXBWFT are produced by rolling a wooden rod backwards and forwards. Place two solid barriers in the water with a gap between them. Water diracts as it passes through the barrier and spreads out. e smaller the barrier, the more the amount of EJSBDUJPO4UVEFOUTTIPVMEOPUFUIBUUIFXBWFMFOHUITUBZTUIFTBNFBOEUIF curvature of the diracted waves is centred at the middle of the gap. Because the wavelength of light is so small, it is dicult to show the diraction of light. It can be done using talcum powder and microscope slides and students should be able to do this for themselves. Interference can be shown by having two gaps in the barrier in the water trough. Again, it is dicult to show interference in light because of the short wavelength. 4UVEFOUTNBZCFGBNJMJBSXJUI interference of radio waves if they can hear another radio Waves barrier station as well as the one they are trying to listen to. is is caused because the two stations are broadcasting POTJNJMBSGSFRVFODJFT6TVBMMZUIJTEPFTOPUNBUUFSCFDBVTFUIFUXPTUBUJPOTBSF far enough away, but sometimes atmospheric conditions are such that the radio signals can interfere. Interference in sound can easily be demonstrated with two loudspeakers connected to the same signal generator. e distance between the loudspeakers should be about two to three metres. Ask students to walk in a straight line in front of the loudspeakers from one to the other. ey should hear alternate loud BOERVJFUOPUFT Grade 9 105 6OJU8BWFNPUJPOBOETPVOE SA = starter activity MA = main activity CA = concluding activity The wave equation SA 4UVEFOUTXPSLXJUIBQBSUOFSUPTVNNBSJTF4UVEFOUTh#PPLQBHFTo MA "DUJWJUZ CA 4UVEFOUTEJTDVTTUIFXPSLFEFYBNQMFTXJUIBQBSUOFS Reflection and refraction SA 4UVEFOUTXPSLXJUIBQBSUOFSUPMJTUBTNBOZFYBNQMFTPGSFGMFDUJPOJOOBUVSF MA *OTNBMMHSPVQTTUVEFOUTFYQMPSFSFGMFDUJPOPGMJHIUXBWFTBOESFGSBDUJPO EFTDSJCFEPOQBHFToPGUIJTCPPL CA 4UVEFOUTXPSLXJUIBQBSUOFSUPTVNNBSJTF4UVEFOUTh#PPLQBHFT¦ Diffraction SA 4UVEFOUTXPSLJOTNBMMHSPVQTUPFYQMPSFEJGGSBDUJPOPGXBUFSXBWFTJOBSJQ MA "DUJWJUZ CA 4UVEFOUTXPSLXJUIBQBSUOFSUPNBLFBQPTUFSBCPVUEJGGSBDUJPO Interference SA *OQBJSTTUVEFOUTEJTDVTTUIFNFBOJOHPGUIFUFSNAJOUFSGFSFODF-FBEUIFNUPEJTD JOUFSGFSFODFPGSBEJPTUBUJPOTBTBOFWFSZEBZFYBNQMF MA *OTNBMMHSPVQTTUVEFOUTFYQMPSFJOUFSGFSFODFPGXBUFSXBWFTVTJOHBSJQQM CA 3FWJFXRVFTUJPOTUPCFUBDLMFEXJUIBQBSUOFS Activities t1MPUUIFQBUIPGMJHIUBTJUJTSFFDUFEGSPNBNJSSPSBOENFBTVSFBOH incidence and reection. t1MPUUIFQBUIPGMJHIUBTJUQBTTFTUISPVHIBHMBTTCMPDL Resources IUUQUIFPSZVXJOOJQFHDBNPE@UFDINPEFIUNM Where next? e next section looks at sound as a wave and investigates some of its properties BOEBQQMJDBUJPOT6MUSBTPVOEJTTPVOEUIBUIBTBGSFRVFODZBCPWFU hearing but can be heard by some animals. It has practical applications for humans as well, and these are examined. Answers to review questions NT 2. 4 m .)[ 3FFDUJPOJTCPVODJOHCBDLPGXBWFTGSPNBTVSGBDFSFGSBDUJPOJTE and change in speed of a wave as it passes from one material into another; diraction is spreading out of a wave as it passes through a gap or past the edge of an obstacle; interference is the reinforcement or cancellation of two waves as they pass one another 106 Grade 9 6OJU8BWFNPUJPOBOETPVOE 4PVOEXBWFT Learning Competencies 5IJTTFDUJPO TIPVME GJMMBQQSPYJNBUFMZ 5 periods of UFBDIJOHUJNF #ZUIFFOEPGUIJTTFDUJPOTUVEFOUTTIPVMECFBCMFUP t *EFOUJGZTPVOEXBWFTBTMPOHJUVEJOBMNFDIBOJDBMXBWFTBOEEFTDSJCFIPX UIFXBWFTBSFTQSPEVDFEBOEIPXUIFZQSPQBHBUF t $PNQBSFUIFTQFFEPGTPVOEJOEJGGFSFOUNBUFSJBMTBOEEFUFSNJOFUIF TQFFEPGTPVOEJOBJSBUBHJWFOUFNQFSBUVSF t %FGJOFUIFJOUFOTJUZPGBTPVOEXBWFBOETPMWFQSPCMFNTVTJOHUIF JOUFOTJUZGPSNVMB t &YQMBJOUIFNFBOJOHPGUIFUFSNTFDIPSFWFSCFSBUJPOQJUDIMPVEOFTTBOE RVBMJUZ t &YQMBJOUIFSFGMFDUJPOBOESFGSBDUJPOPGTPVOEBOEEFTDSJCFTPNF BQQMJDBUJPOT Starting off is section builds on the understanding that sound is a longitudinal wave. It examines how sounds are produced and how sounds are heard. Not all animals SFTQPOEUPTPVOEJOUIFTBNFXBZ3FFDUJPOPGTPVOEJTDPOTJEFSFEJONPSF detail and this leads on to an appreciation of how the reection of ultrasound allows doctors and midwives to monitor the progress of an unborn baby in its NPUIFSTXPNC Teaching notes Activity 8.9: Answer Begin by asking the students how sound is produced. All of their answers can 4UVEFOUThPXO CFTVNNBSJTFEBTCFJOHBNFDIBOJDBMWJCSBUJPOPGPOFGPSNPSBOPUIFS 4VDI results WJCSBUJPOTOFFEBNFEJVNUISPVHIXIJDIUIFZDBOUSBWFM4UVEFOUTDBOVTFB TUSJOHUFMFQIPOFUPDPNNVOJDBUFRVJUFMBSHFEJTUBODFT"XBUDIPOUIFUBCMFTFFNT Activity 8.10: UPCFBMPUMPVEFSJGZPVQMBDFZPVSFBSPOUIFUBCMF4PVOEUSBWFMT NPSF FBTJMZ Answer through denser materials. 4UVEFOUThPXO e American Indian scouts used to be able to detect the sound of horsemen long results before they could be seen. By putting their ear to the ground they could hear the hoof beats. If possible, show that sound does not travel through a vacuum. Activity 8.11: Answer FSFBSFTFWFSBMXBZTUPTIPXUIBUTPVOEJTBMPOHJUVEJOBMXBWF3FNPWF UIF PXO 4UVEFOUTh ends from a can. Cover one end of the can with rubber from a balloon. Make sure results the rubber is tight and held rmly in place. Place a loudspeaker at the other end. )BOHBUBCMFUFOOJTCBMMPOBOFUISFBETPUIBUJUKVTUUPVDIFTUIFSVCCFS8IFO the loudspeaker is turned on, the table tennis ball vibrates. As well as showingActivity that 8.12: Answer sound is a vibration, it demonstrates the principle of the ear. e sound passes down the ear canal and vibrates the eardrum. 4UVEFOUThPXO 4IPXIPXUPOEUIFBVEJCMFSBOHF&BDITUVEFOUXJMMIBWFBTMJHIUMZresults EJFSFOU SBOHFCVUXJMMCFBQQSPYJNBUFMZ)[UPL)[*UJTMJLFMZUIBUUIFUFBDIFSXJMM Grade 9 107 6OJU8BWFNPUJPOBOETPVOE Activity 8.13: Answer TUPSNN EFMBZEFDSFBTFT Activity 8.14: Answer NT Activity 8.15: Answer 4UVEFOUThPXO results Activity 8.16: Answer XBUFSEFQUIN OPUCFBCMFUPIFBSUIFIJHIFSGSFRVFODZOPUFTBTBVEJCMFSBOHFEPFTS BHF5PNBLFTVSFUIBUTUVEFOUTSFBMMZDBOIFBSUIFWFSZIJHIGSFRVFODJ USZUPDMBJNSFQFBUUIFFYQFSJNFOUTUBSUJOHBUL)[BOESFEVDFUIFGSF but have the signal generator turned o! Discuss with the students the eect density of material and temperature of gas have on the speed of sound. In general, denser materials have their particles closer UPHFUIFSTPUIFWJCSBUJPOTBSFQBTTFEPONPSFRVJDLMZ"TUIFUFNQFSBU gas increases, the speed of sound also increases. is is due to the average kinetic FOFSHZPGUIFQBSUJDMFTJODSFBTJOH3FNJOETUVEFOUTUIBUUIJTXBTEJT Unit 7. 4UVEFOUTDBONFBTVSFUIFTQFFEPGTPVOEVTJOHSFFDUJPOGSPNBUBMM FSFFDUJPOPGTPVOEJTDBMMFEBOFDIP*UJTQPTTJCMFUPPCUBJORVJUFBO WBMVF"TLTUVEFOUTUPJNBHJOFUIFZBSFUJNJOHBNSBDFFZBSFPOUIF nishing line. Do they start their stopwatch when they hear the starting pistol or XIFOUIFZTFFUIFQVPGTNPLF )PXGBSPVUXPVMEUIFZCFJGUIFZTUBSUFEUIF stopwatch when they heard the gun? Introduce the idea of Mach numbers as being how many times faster than sound something travels. FSFBSFQMBDFTXIFSFSFFDUJPOPGTPVOEJTBOVJTBODF3FDPSEJOHTUVEJ DJOFNBTBOEUIFBUSFTOFFEUPSFEVDFFDIPFTUPBNJOJNVN)BSETPMJETVS reect sound very well; so ones absorb the sound. is is why there is usually a MPUPGDVSUBJOJOHUZQFNBUFSJBMJOUIFBUSFTBOEDJOFNBT3FDPSEJOH special tiles on the walls and ceiling to absorb unwanted sound. 4IPXTUVEFOUTIPXBTPVOEXBWFJTEJTQMBZFEPOBOPTDJMMPTDPQFXJUIU of a microphone. is is a transverse wave representing a longitudinal wave. It is important that students appreciate this. is representation allows us to look more closely at some of the sounds we hear every day. Using a variety of musical instruments, the same note can be played and its shape looked at. Although UIFGSFRVFODZPGUIFOPUFSFNBJOTUIFTBNFUIFTIBQFPGUIFXBWFEFUFSN JUTRVBMJUZPSUJNCSF.VTJDBMOPUFTBSFDPNQMFYBOENBEFVQPGBOVN EJFSFOU GSFRVFODJFT BTXFMM BTUIFNBJOGSFRVFODZ FTF GSFRVFODJFT BEEUPHFUIFS to produce the complex shape. %JTDVTTXJUITUVEFOUTIPXUIFJOUFOTJUZPGTPVOEWBSJFTXJUIEJTUBOD PCFZTBOJOWFSTFTRVBSFMBXJTJTPOFPGNBOZTVDIMBXTJOQIZTJDT 6MUSBTPVOEJTEFOFEBTTPVOEXJUIBGSFRVFODZBCPWFIVNBOIFBSJOH-J waves, sound is reected and refracted. Ultrasound is used at sea to monitor the depth of the sea bed, search for wrecks and sh as well as enemy submarines. FIJHIGSFRVFODZTPVOEJTVTFEUPDMFBOEFMJDBUFJOTUSVNFOUTBOEKF vibrating water in a tank. It is also used to treat muscles and destroy gallstones and kidney stones. Most students will know of ultrasound scanning for monitoring the foetus, but it is used for general body scanning as well. It is important to stress that ultrasound produces an image of the foetus in the womb. It is not a photograph, as the image is not produced using light. Ultrasound is reected back as it strikes dierent surfaces in the foetus. e dierent times for the reected sound pulses to reach the detector allow an image to be built up. 108 Grade 9 6OJU8BWFNPUJPOBOETPVOE SA = starter activity MA = main activity CA = concluding activity Sound waves SA *OQBJSTTUVEFOUTEJTDVTTIPXTPVOEJTQSPEVDFE'FFECBDLJEFBT MA "DUJWJUZ "DUJWJUZ "DUJWJUZ CA 4UVEFOUTXSJUFSFQPSUTPOUIFBDUJWJUJFTDBSSJFEPVUJOUIJTMFTTPO Hearing and the speed of sound SA "DUJWJUZ MA "DUJWJUZ "DUJWJUZ CA 4UVEFOUTXSJUFSFQPSUTPOUIFBDUJWJUJFTDBSSJFEPVUJOUIJTMFTTPO Describing sound waves SA *OTNBMMHSPVQTTUVEFOUTMJTUFYBNQMFTPGTJUVBUJPOTXIFSFUIFSFGMFDUJPOP OVJTBODF MA "DUJWJUZ CA *OQBJSTTUVEFOUTQSPEVDFBQPTUFSTIPXJOHUIFDIBSBDUFSJTUJDTPGTPVOEXBWF PGUIF4UVEFOUTh#PPL Intensity of sound waves SA *GQPTTJCMFTUVEFOUTXPSLPVUTJEFJOQBJSTUPFYQMPSFIPXJOUFOTJUZPGTPVOEW EJTUBODFTFF4UVEFOUTh#PPLQBHF MA 4UVEFOUTUPXPSLJOQBJSTUPTVNNBSJTF4UVEFOUTh#PPLQBHFT¦ CA 3FWJFXRVFTUJPOT¦UPCFUBDLMFEXJUIBQBSUOFS Uses of sound waves SA 4UVEFOUTUPXPSLJOQBJSTUPEJTDVTTVTFTPGTPVOEXBWFTBOEQSPEVDFBQPTUFS JOGPSNBUJPO MA "DUJWJUZ *OQBJSTTUVEFOUTSFTFBSDIXIJDIBOJNBMTJO&UIJPQJBDBOIFBSVMUSBTPVOE CA 3FWJFXRVFTUJPOUPCFUBDLMFEJOQBJST &OEPGVOJURVFTUJPOTUPCFUBDLMFEJOQBJST Activities t'JOEPVUUIFBVEJCMFSBOHFTPGOBUJWF&UIJPQJBOBOJNBMT8IBUBOJNBMTDBO hear ultrasound? t.FBTVSFUIFTQFFEPGTPVOE Resources IUUQXXXNFEJBDPMMFHFDPNBVEJPTPVOEXBWFTIUNM Grade 9 109 6OJU8BWFNPUJPOBOETPVOE Answers to review questions B 4PVOEUSBWFMTGBTUFSUISPVHITPMJETUIBOMJRVJETGBTUFSUISPV gases. C4PVOEUSBWFMTGBTUFSJOXBSNBJSUIBODPME -PVEOFTTJTUIFBNQMJUVEFPGBTPVOEXBWFQJUDIJTUIFGSFRVFODZPGO timbre is the shape of note that gives an instrument its characteristic sound. 2 B8N C8N 2 D8N 2 4. a) 36 W/m2 b) 1.44 W/m2 #PEZTDBOOJOHGPFUBMNPOJUPSJOHEFTUSPZJOHHBMMTUPOFTLJEOFZ cleaning delicate instruments/jewellery. Answers to end of unit questions 1. a) transverse b) longitudinal c) parallel to wave direction d) transverse: light, water, electromagnetic, named electromagnetic; longitudinal: sound, ultrasound e) transverse: vibrate slinky side to side; longitudinal: vibrate slinky along its length XBWFMFOHUINQFSJPET GSFRVFODZ)[XBWFMFOHUIN TQFFENTQFSJPET Q)[oCPSEFSCFUXFFOVMUSBWJPMFUBOE9SBZT 4. a) refraction b) diraction c) interference d) reection Constructive + = Destructive + = DNDN 110 Grade 9 6OJU8BWFNPUJPOBOETPVOE 4PVOEIBTBXBWFMFOHUIPGBTJNJMBSPSEFSPGNBHOJUVEFUPUIFEPPSXJEUITP it diracts easily around the door. 8. reected sound N 4UBOEBEJTUBODFPGBCPVUNGSPNBUBMMCVJMEJOHDMBQQJFDFTPGXPPE together in time with the echo, time for ten claps, work out the time for one DMBQTQFFEEJTUBODF× 2/time NT 12.speed of light much greater than speed of sound T Grade 9 111 Minimum learning competencies Area of competency Grade 9 Grade 9 Vectors t3FQSFTFOUWFDUPSTBOBMZUJDBMMZBOEHSBQIJDBMMZ 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t%FTDSJCFEFWJDFTVTFEUPNFBTVSFQSFTTVSFBOEQSFTTVSFEJFSFO t%FTDSJCFUIFSFMBUJPOTIJQCFUXFFOHBVHFQSFTTVSFBCTPMVUFQS BUNPTQIFSJDQSFTTVSF t%FNPOTUSBUFTDJFOUJDFORVJSZTLJMMTTVDIBTPCTFSWJOHDPNNV DPNQBSJOHNFBTVSJOHBTLJOHRVFTUJPOTEFTJHOJOHFYQFSJNFOU DPODFQUTQSPCMFNTPMWJOH 114 Grade 9 Grade 9: Physics Minimum Learning Competencies Temperature and heat t$PNQBSFIFBUBOEUFNQFSBUVSF t&YQMBJOBCPVUUIFSNBMFYQBOTJPOPGTPMJETMJRVJETBOEHBTFT t*EFOUJGZVOJUTVTFEUPNFBTVSFFOFSHZJOUIFSNBMTZTUFNT t4PMWFQSPCMFNTJOWPMWJOHMJOFBSBSFBMBOEWPMVNFFYQBOT t4PMWFQSPCMFNTSFMBUFEUPFYQBOTJPOPGMJRVJET t%FOFUIFUFSNTTQFDJDIFBUDBQBDJUZIFBUDBQBDJUZBOEMBUFOUI t4UBUFUIFMBXPGIFBUFYDIBOHF t4PMWFQSPCMFNTJOWPMWJOHIFBUFYDIBOHF t%FNPOTUSBUFTDJFOUJDJORVJSZTLJMMTTVDIBTPCTFSWJOHDPNN DPNQBSJOHNFBTVSJOHJOGFSSJOHNBLJOHDPODMVTJPOTQSPCMF BQQMZJOHDPODFQUTBOEEFTJHOJOHFYQFSJNFOUT Wave motion and sound t%FOFUIFUFSNTXBWFQVMTFUSBJOPGXBWFT t%JFSFOUJBUFCFUXFFONFDIBOJDBMBOEFMFDUSPNBHOFUJDXBWF FYBNQMFTPGFBDI t*EFOUJGZXBWFTBTUSBOTWFSTFBOEMPOHJUVEJOBMBOEHJWFFYB t%FOFUIFUFSNTVTFEUPEFTDSJCFXBWFTDSFTUUSPVHIXBWFMFOHU BNQMJUVEF t6TFXBWFTQFFEGPSNVMBUPTPMWFQSPCMFNTSFMBUFEUPXBWFNP t%FTDSJCFUIFDPNNPOQSPQFSUJFTPGXBWFTSFFDUJPOSFGSBDUJP EJSBDUJPOBOEJOUFSGFSFODF t%FTDSJCFUIFQSPEVDUJPOBOEQSPQBHBUJPOPGTPVOE t$PNQBSFUIFTQFFETPGTPVOEJOEJFSFOUNFEJB t%FUFSNJOFUIFTQFFEPGTPVOEJOBJSBUBOZHJWFUFNQFSBUVSF t&YQMBJOSFFDUJPOSFGSBDUJPOEJSBDUJPOBOEJOUFSGFSFODFPG t-JTUTPNFBQQMJDBUJPOTPGSFFDUJPOTPGTPVOE t%FOFUIFUFSNTVTFEUPEFTDSJCFUIFDIBSBDUFSJTUJDTPGTPVOE t%FNPOTUSBUFTDJFOUJDJORVJSZTLJMMTBTPCTFSWJOHDMBTTJGZ DPNNVOJDBUJOHDPNQBSJOHBTLJOHRVFTUJPOTNFBTVSJOHBOEB DPODFQUT Grade 9 115 Physics syllabus General objectives of Grade 9 physics t6OEFSTUBOEUIFCBTJDDPODFQUTPGQIZTJDTUIFMBXTPGEZOBNJDTBOE EJFSFOULJOETPGGPSDFTUIFRVBOUJDBUJPOBOEGPSNTPGFOFSHZNFD TPVOEMJHIUUIFSNBMBOEUIFXBZFOFSHZJTUSBOTGPSNFEBOEUSBOTN UIFDPODFQUTBOEVOJUTSFMBUFEUPFOFSHZXPSLBOEQPXFSBOEUIFMB PGDPOTFSWBUJPOPGFOFSHZBOEPGNPNFOUVNGPSPCKFDUTNPWJOH EJNFOTJPO t%FWFMPQNBOJQVMBUJWFTLJMMTJOTPMWJOHQSPCMFNTSFMBUFEUP DPOTFSWBUJPOPGNPNFOUVNBOEFOFSHZ t6OEFSTUBOEUIFQSPQFSUJFTPGNFDIBOJDBMXBWFTBOETPVOEBOEUIFQ VOEFSMZJOHUIFQSPEVDUJPOBOEUSBOTNJTTJPOPGNFDIBOJDBMXBW UIFQSPQFSUJFTPGMJHIUBOEUIFQSJODJQMFTVOEFSMZJOHUIFUSBOTN UISPVHIBNFEJVNBOEGSPNPOFNFEJVNUPBOPUIFS t%FWFMPQTDJFOUJDJORVJSZTLJMMTBTUIFZWFSJGZBDDFQUFEMBXTBO BTTJHOFEQSPCMFNTBOEUIPTFFNFSHJOHGSPNUIFJSJOWFTUJHBUJPO t"OBMZTFUIFJOUFSSFMBUJPOTIJQTCFUXFFOQIZTJDTBOEUFDIOPMPHZB UIFJNQBDUPGUFDIOPMPHJDBMBQQMJDBUJPOTPGQIZTJDTPOTPDJFUZ FOWJSPONFOU t4PMWFUIFQSPCMFNTVTJOHBWBSJFUZPGQSPCMFNTPMWJOHTLJMMT Unit 1: Vectors (9 periods) Unit outcomes: Students will be able to: t"DRVJSFLOPXMFEHFBOEVOEFSTUBOEJOHTPGWFDUPSSFQSFTFOUBUJP BEEJUJPOBOETVCUSBDUJPOBOEQSPQFSUJFTPGWFDUPST t%FWFMPQTLJMMTPGSFTPMWJOHBOEDPNQPTJOHWFDUPST t%FWFMPQJOUFSFTUJOTPMWJOHQSPCMFNTVTJOHUIFWFDUPSBQQSPB 116 Grade 9 Grade 9: Physics syllabus Competencies Contents Suggested activities Students will be able to: 1. Vectors :PVOFFEBSFWJFXPOWFDUPST t %FåOFUIFUFSNWFDUPS 1.1 Representation of 7FDUPSTBSFSFBMCVUJOWJTJCMF t 3FQSFTFOUWFDUPSTvectors (2 periods) 5IJTTIPVMETUBSUPGGUIJTVOJU5IFJEFBPGASFBMJUZ BOBMZUJDBMMZ t "OBMZUJDBM PGUIFVOTFFOJTJNQPSUBOU4UVEFOUTTIPVMEMJTUB UIFDPODFQUTJOQIZTJDTUIBUBSFAVOTFFOCVUNVTU t 3FQSFTFOUWFDUPSTt(SBQIJDBM CFSFBM4UVEFOUTTIPVMECFBCMFUPBEEBOETVCUSB HSBQIJDBMMZ WFDUPSTHSBQIJDBMMZCZUIFUJQUPUBJMNFUIPEPSU t "EEUXPWFDUPSTBMPOH 1.2 Addition and QBSBMMFMPHSBNNFUIPE the same direction, in subtraction of vectors. "DUJWJUZUIFUFBDIFSNBLFTVQTFWFSBMA.ZTUFSZQB opposite directions and (5 periods) UIBUJODMVEFEJSFDUJPOTMJLFA&BTUNGSPNBTUBSU at right angles to each t(SBQIJDBMMZ QPJOU/PSUINUIFOXFTUNUIFOTPVUIN PUIFS t#ZDPNQPOFOUNFUIPET 5IFO&BTUN4UVEFOUTBDUPVUUIFEJSFDUJPOTJOUIF t 4QFDJGZUIFEJSFDUJPO QSPCMFN8IFOUIFQSPCMFNJTDPNQMFUFEUIFZNFBTV PGUIFSFTVMUBOUWFDUPST 1.3 Some applications of UIFEJTUBODFGSPNUIFTUBSUJOHQPJOU5IFZDPQZUIF VTJOHBOBOHMF QSPCMFNEPXOBOEEPJUPOHSBQIQBQFS5IFZNFBTVSF vectors (2 periods) t 3FTPMWFWFDUPSTJOUP UIFEJTUBODFXJUIBTDBMFPGPOFCPYN t&RVJMJCSJVN SFDUBOHVMBSDPNQPOFOUT 6TJOHUIFUIFPSFNPG1ZUIBHPSBTUIFZTPMWFUIFQSPC t 'JOEUIFNBHOJUVEF t&YQFSJNFOUBMBQQSPBDI NBUIFNBUJDBMMZBOEDPNQBSFBOTXFST BOEEJSFDUJPOPGUIF 1SPCMFNTPMWJOHMFUUIFTUVEFOUTTPMWFHSBQIJD SFTVMUBOUPGUXPPS BEEJUJPOPSTVCUSBDUJPOPGWFDUPST5IFZTIPVMEC NPSFWFDUPSTVTJOHUIF BCMFUPFYQSFTTUIFSFTVMUBOUVTJOHUIFUIFPSFNPG DPNQPOFOUNFUIPE 1ZUIBHPSBTJOUFSQSFUFEGSPNHSBQIQBQFS t 6TFR=(Rx2 + Ry2) %PMPUTPGQFFSJOTUSVDUJPOPOGPSDFTBOEBEEJOH to determine the 5IJTJTNVDINPSFFGåDJFOUUIBOCPBSEXPSL NBHOJUVEFPGUIF SFTVMUBOUWFDUPST Sample: Peer instruction: t "QQMZUBOæ= Is this system in equilibrium? y/RxRto determine the direction PGUIFSFTVMUBOUWFDUPST t 'JOEUIFBOHMFPGUIF SFTVMUBOUWFDUPSR makes with respect to the QPTJUJWFxBYJT ZFT t 6TFUIFBQQSPQSJBUFTJHO DPOWFOUJPOPGWFDUPS 2) no components in the 4PNFXJMMDPNQMBJOUIBUUIFTJEFTBSFOPUQBSBMMF TPMVUJPOPGQSPCMFNT 5IFUJQUPUBJMCSJOHTBTVNPG[FSPTPZFT t %FåOFUIFUFSN 5XPGPSDFWFDUPSTBDUJOHPOBOPCKFDUDBOBEEUP FRVJMJCSJVN NBLJOHFRVJMJCSJVN*TJUQPTTJCMFGPSUISFFGPSDF BEEUPBTVNPG[FSP ZFT 2) no &YQMBJOJOHSPVQT F x = 0, F y = 0 Grade 9 117 Grade 9: Physics syllabus Competencies Contents Suggested activities t6TFUIFTJHNBOPUBUJPO *OWJUFTUVEFOUTUPNBLFVQUIFJSPXOGPSDFWFDUPST UXPEJNFOTJPOTUIBUBEEVQUP[FSP*OWJUFUIFNUPQVU UIFNJOUPUIFFRVBUJPOXJUIUIFTJHNBT 4UFQPOF5ISFFGPSDFTJOYEJSFDUJPOUXPJOZ 4UFQUXPGPVSGPSDFTJOYEJSFDUJPOUISFFJOZ 4UFQUISFFGPSDFTBU°¦°°BOE¦° all adding UP[FSP4UVEFOUTNVTUEFNPOTUSBUFUIFLOPXMFEHFPG DPNQPOFOUWFDUPST Peer instruction on equilibrium or non-equilibrium 4FF.B[VSGPSNBOZFYBNQMFT 1VUVQBWFDUPSESBXJOH Is this system in equilibrium or not? 4UVEFOUTWPUF Assessment FUFBDIFSTIPVMEBTTFTTFBDITUVEFOUTXPSLDPOUJOVPVTMZPWFSUIFXIP BOEDPNQBSFJUXJUIUIFGPMMPXJOHEFTDSJQUJPOCBTFEPOUIFDPNQFUF EFUFSNJOFXIFUIFSUIFTUVEFOUIBTBDIJFWFEUIFNJOJNVNSFRVJSFEMFWF Students at minimum requirement level 4UVEFOUXPSLJOHBUUIFNJOJNVNSFRVJSFNFOUMFWFMXJMMCFBCMFUPE EFTDSJCFDPODFQUTSFMBUFEUPWFDUPSTTDBMBSTSFQSFTFOUBUJPOPG BOETVCUSBDUJPOPGWFDUPSTDPOEJUJPOPGFRVJMJCSJVNBQQMZNBUIF TVDIBTUIF1ZUIBHPSFBOFPSFNBOEUSJHPOPNFUSJDSFMBUJPOTIJQTJOTP WFDUPSQSPCMFNTSFTPMWFBWFDUPSJOUPJUTUXPJOEFQFOEFOUDPNQ EFUFSNJOFUIFSFTVMUBOUWFDUPSPGUXPPSNPSFOPOQFSQFOEJDVMBS JOUXPEJNFOTJPOTVTJOHUIFWFDUPSDPNQPOFOUNFUIPE Students above minimum requirement level 4UVEFOUTXPSLJOHBCPWFUIFNJOJNVNSFRVJSFNFOUMFWFMTIPVMECFQS UIFJSBDIJFWFNFOUTSFDPHOJTFEFZTIPVMECFFODPVSBHFEUPDPOUJOVF IBSEBOEOPUCFDPNFDPNQMBDFOU Students below minimum requirement level 4UVEFOUTXPSLJOHCFMPXUIFNJOJNVNSFRVJSFNFOUMFWFMXJMMSFRVJS UIFZBSFUPDBUDIVQXJUISFTUPGUIFDMBTTFZTIPVMECFHJWFOFYUSBBUUF DMBTTBOEBEEJUJPOBMMFTTPOUJNFEVSJOHCSFBLTPSBUUIFFOEPGUIFE 118 Grade 9 Grade 9: Physics syllabus Unit 2: Motion in a straight line (12 periods) Unit Outcomes: Students will be able to: t(BJOLOPXMFEHFBOEVOEFSTUBOEJOHPOVOJGPSNBOEVOJGPSNMZBDDFMFSBUFE NPUJPOBOEBCPVUSFMBUJWFWFMPDJUZJOPOFEJNFOTJPO t%FWFMPQTLJMMTJOBQQMZJOHFRVBUJPOTPGVOJGPSNMZBDDFMFSBUFENPUJPOJO TPMWJOHQSPCMFNT t%FWFMPQTLJMMTJOESBXJOHBOEJOUFSQSFUJOHHSBQITSFQSFTFOUJOHVOJGPSNBOE VOJGPSNMZBDDFMFSBUFENPUJPO t"QQSFDJBUFUIFNBUIFNBUJDBMBOEHSBQIJDBMSFQSFTFOUBUJPOPGNPUJPO t%FNPOTUSBUFBOVOEFSTUBOEJOHPGEJFSFOULJOETPGNPUJPOBOEPGUIF RVBOUJUBUJWFSFMBUJPOTIJQTCFUXFFOEJTQMBDFNFOUWFMPDJUZBOEBDDFMFSBUJPO BOETPMWFTJNQMFQSPCMFNTJOWPMWJOHEJTQMBDFNFOUWFMPDJUZBOEBDDFMFSBUJ t%FTJHOBOEDPOEVDUJOWFTUJHBUJPOTPOUIFEJTQMBDFNFOUWFMPDJUZBOE BDDFMFSBUJPOPGBOPCKFDUBOBMZTFFWFSZEBZQIFOPNFOBJOUFSNTPGUIF NPUJPOTJOWPMWFE Competencies Contents Students will be able 2. Motion in a to: straight line t &YQMBJOUIF 2.1 Uniform motion terms distance, (2 periods) displacement, TQFFEWFMPDJUZBOE 2.2 Uniformly BDDFMFSBUJPO accelerated motion t &YQMBJOUIF (2 periods) EJGGFSFODFCFUXFFO distance and EJTQMBDFNFOU 2.3 Graphical description of t %JTUJOHVJTI uniformly accelerated between constant, motion (2 periods) instantaneous and t'SFFGBMMNPUJPO BWFSBHFTQFFEBOE between constant, instantaneous and 2.4 Equations of BWFSBHFWFMPDJUZ uniformly accelerated BOEHJWFFYBNQMFT motion QFSJPET JOWPMWJOHVOJGPSN BOEOPOVOJGPSN 2.5 Relative velocity NPUJPO in one dimension t %SBXHSBQITPGS (2 periods) WTt, VWTt, and a WTt graphs using SFDPSEFEEBUB t $PNQMFUFUIFSWT tUBCMFHJWFOTPNF JOJUJBMJOGPSNBUJPO Grade 9 Suggested activities The teacher should use the Human Measuring Line %BUBBOBMZTJT 5IFLFZJEFBJTDSFBUJOHUIFBDDVSBUFWFMPDJUZWTUJNFH *OQSFWJPVTVOJUT(SBEFTBOEXFKVTUQMPUUFEBWFSBHF WFMPDJUZWFSTVTUJNF5IJTDIBQUFSUBLFTBEFFQFSMPPL BWFSBHFWFMPDJUZSFBMMZJTUIFJOTUBOUBOFPVTWFMP QPJOU "DUJWJUZ .PEFMUIJTXJUIBQFSTPOXBMLJOHCFUXFFOUXPQPJOUTFW XJUIBWFSZVOFWFOWFMPDJUZJODMVEJOHCBDLXBSET5IF POMZSVMFTBSFUIBUBGUFSTFDPOETUIFTUVEFOUNVTUCF the endpoint and DN"TLTPNFPOFUPEPBRVBMJUBUJWF HSBQIBUUIFTBNFUJNFBTUIFXBMLJOHPGWTU*UNJHIU CFRVJUFKBHHFEBOEOPOMJOFBSFWFODSPTTJOHUIFBYJT TIPXCBDLXBSETNPUJPO%PBOPUIFSKBHHFEXBMLVOEFSUI same conditions tTBOEdN5IFBWFSBHFWFMPDJUZJT DBMDVMBUFEGSPND/TBOEDPNQBSFEUPUIFRVBMJUBUJW "UTPNFQPJOUJOUIFUJNFUIFQFSTPO.645IBWFHPOFBU UIFBWFSBHFWFMPDJUZUIPVHIUIFJOTUBOUBOFPVTWFMPD DPOTUBOUMZDIBOHJOH8IBUQPJOUXFEPOULOPXCVUWFM NVTUCFBDPOUJOVPVTHSBQI:PVDBOOPUJOTUBOUBOFPVT KVNQGSPNPOFQMBDFUPBOPUIFS*OTUBOUBOFPVTWFMPD CFJNNFBTVSBCMFCVUUIFSFBSFXBZTUPDBMDVMBUFJU t *GUIFWFMPDJUZJTDPOTUBOUMZJODSFBTJOHPWFSBOJO OPKBHHFENPUJPOTUIFOUIFBWFSBHFWFMPDJUZNVTUCF JOTUBOUBOFPVTWFMPDJUZBUUIFUJNFNJEQPJOU5IJTJT JEFB*UGVOEBNFOUBMMZJTUIFNFBOWBMVFUIFPSFNGPS as Vinstant at t mid (mid GVODUJPOT6TFUIJTJEFBUPLOPXV BWH point) 5IJTXJMMHJWFZPVBOFYDFMMFOUXBZUPDBMDVMBUFWJB UIFBDDFMFSBUJPO 119 Grade 9: Physics syllabus Competencies Contents Students will be able to: t 4PMWFQSPCMFNTVTJOH SWTt and VWTt HSBQIT t %FUFSNJOFUIF distance and EJTQMBDFNFOUPGB CPEZGSPNHSBQIJDBM SFQSFTFOUBUJPOPG NPUJPO 120 Suggested activities "DUJWJUZ4UBSUPVUXJUIUIFIVNBONFBTVSJOHMJOF %PTFWFSBMFYQFSJNFOUTXJUIEJGGFSFOUTQFFET .BLFEPUQMPUT Peer instruction: 8IBUJTUIFBWFSBHFWFMPDJUZPOBEPUQMPU 4VNPGBMMWFMPDJUJFTPGUIFJOUFSWBMOPPGJOUFSWBMT )PXEPFTUIJTDPNQBSFXJUIUIFBWFSBHFWFMPDJUZJOFBDI JOUFSWBM B "WFSBHFWFMPDJUJFTJOFBDIJOUFSWBMBSFUIFTBNFBTUI BWFSBHFGPSUIFXIPMFJOUFSWBM C %JGGFSFOUGSPNUIFBWFSBHFWFMPDJUZGPSUIFJOUFSW -FUUIFTUVEFOUTWPUFBOEEJTDVTTUPBSSJWFBUUIFDPSSF BOTXFS %PUQMPUTGPSTFHNFOUFENPUJPO "DUJWJUZTUVEFOUTNBLFVQUIFJSPXOTUPSJFTBCPVUNPUJP $POTUSBJOUTUIFZNVTUVTFWFMPDJUJFTPGPOMZLNTLNT LNTS¦LNTPS¦LNTPSLNT Graph one: make a vWTtHSBQIGPSUIFJSTUPSZ4UVEFOUTNBLF UIFHSBQITWFSZBDDVSBUFMZ5ISFFHSPVQTPGTUVEFOUToFB HJWFUIFUFBDIFSUIFJSvWTt graphs; then they stand up and HJWFUIFWFSCBMEFTDSJQUJPOPGUIFJSNPUJPO5IFSFTUPGU DMBTTNBUDIFTUIFWFSCBMEFTDSJQUJPOXJUIUIFHSBQIT3FQ UIFQSPDFTT%PUIFTBNFBDUJWJUZXJUIUIFDPOTUSBJOUUIBU QFSTPONVTUHFUCBDLIPNFBGUFSUIFUSBWFMT4UVEFOUTN DBMDVMBUFIPXGBSIFXFOUUIFOHPCBDLXBSETUPHFUIPNF BHBJO 5&95/PUFUIFUFYUNVTUHJWFUIFSBUJPOBMGPSUIFBSFB under a vWTtQMPUUPCFUIFEJTUBODFUSBWFMMFE *%&"JOTFSUTPNFPG/FXUPOTSFBTPOJOH-FUVTBTTVNFUIBU XFMPPLBUBWFSZTNBMMUJNFJOUFSWBM1FSIBQTUIFWFMPD JTOPUMJOFBSMZJODSFBTJOHPSEFDSFBTJOH4UVEFOUTDPO BiNJDSPWJFXwQFFLJOHJOUPBWFSZTNBMMJOUFSWBMPGUJ a vWTtHSBQI5IFBSHVNFOUJTUIBUUIFBWFSBHFWFMPDJUZJO UIBUTNBMMUJNFJOUFSWBMUJNFTUIFUJNFJOUFSWBMNVTU EJTUBODFUSBWFMMFE -BSHFSPSTNBMMFSWFMPDJUZWBMVFTXJMMBWFSBHFPVU U= V %JTUBODFUSBWFMFEJOt BWFSHF UTFHNFOUTUIJTJTUIFBSFBVOEFS *GPOFBEETPGUIF7 BWFSHF the vWTtEJBHSBN5IJTJTUIFTUBSUPGUIFTUVEZPGDBMDVMVT Since vWTtJTDPOTUBOUGPSTJNQMFNPUJPOEJTUBODF USBWFMMFEGPSDPOTUBOUWFMPDJUZJTTJNQMZUIFTVNPG SFDUBOHMFT4PNFSFDUBOHMFTXJMMIBWFOFHBUJWFBSFB Grade 9 Grade 9: Physics syllabus Competencies Contents Suggested activities "DUJWJUZ"DDFMFSBUFENPUJPOVTJOHUIFIVNBOMJOF-FUU students measure a motion that is either accelerating or EFDFMFSBUJOH6TFBCJDZDMFPSBQFSTPOSJEJOHPOBCPB TPNFXIFFMT%FDFMFSBUJPOJTTJNQMFGSJDUJPOXJMMTVG accelerate a person on a wheel one must use a weight pulled CZHSBWJUZ5IFXFJHIUNVTUIBOHPVUBXJOEPXPSPQFSBUF GSPNBQVMMFZGSPNUIFDFJMJOHUXPQVMMFZTBSFOFFEF GPSDFNVTUCFIPSJ[POUBM5IFCJDZDMFJTFBTJFSUPEPJOJU BTJUBDDFMFSBUFTTMPXMZ 3PMMJOHBIFBWZEVNCCFMMGSPNBSBNQHJWFTHPPESFTV EVNCCFMMNVTUCFSFMBUJWFMZTNPPUIBOEUIFQBUITIPVM BCPVUoNFUFST'PSUIFCJDZDMFBOEEVNCCFMMZPVNBZOFF UPBEKVTUUIFUJNFSUPPOFTFDPOEJOUFSWBMTUIPVHITFD JOUFSWBMTJTFBTJFSUPDBQUVSFEBUB&SSPSSBUFTJODS TNBMMFSJOUFSWBMT 4UVEFOUTDSFBUFTFWFSBMEPUQMPUTPGBDDFMFSBUFEP NPUJPO5IFZUSBOTGFSUIFTFUPOPUFCPPLTBOEUIFOUP UBCMFTPGEBUB5IFOUIFZDBMDVMBUFUIFBWFSBHFWFMPD GPSFBDIJOUFSWBMPGUJNF5IFLFZJEFBJTUIBUUIFWFMPDJU JTDIBOHJOHJOTUBOUBOFPVTMZ5IJTJNNFBTVSBCMFRVBO JTDBMMFEJOTUBOUBOFPVTWFMPDJUZ*OBOZUJNFJOUFSW JOTUBOUBOFPVTWFMPDJUZNVTUBUTPNFUJNFEVSJOHUIF JOUFSWBMIBWFUIFTBNFWBMVFBTUIFBWFSBHFWFMPDJUZ JOUFSWBM7FMPDJUZNVTUCFDPOUJOVPVTMZDIBOHJOHOP BSFQFSNJUUFETBZNTUIFOJOTUBOUMZNT = VinstatBUUIFUJNFNJEQPJOU 8FNBLFUIFDMBJNUIBUV BWFSBHF 4UVEFOUTQMPUUIFBWFSBHFWFMPDJUZGPSUIFJOUFSWBM UIFUJNFNJEQPJOU5IJTJTBWFSZJNQPSUBOUJEFB5IFWWT t plot lets us measure something that is immeasurable any PUIFSXBZWJOTUBOU5IJTJTBDPOUJOVFEUIFNFJOQIZTJDT WJFXJOHBOENFBTVSJOHUIFJOWJTJCMF Students construct vWTtQMPUTGPSUIFBDDFMFSBUFENPUJPO 5IFZåOEUIFTMPQFPGUIFMJOFT5IFSFXJMMCFTPNFFSSPS 5IFZåUBMJOFUPUIFJSEBUB*UXJMMCFNPSFBDDVSBUFXIFO UIFPCKFDUJTNPWJOHNPSFTMPXMZBOEMFTTBDDVSBUFXI NPWJOHRVJDLMZ 4UVEFOUTåOEUIFBSFBVOEFSUIFvWTtHSBQI*UTIPVMECF UIFEJTUBODFUSBWFMMFE "DUJWJUZBUUIJTUJNFUIFJOTUSVDUPSHBUIFSTBMMJOGPS GSPNUIFTUVEFOUTBCPVUXIBUUIFZLOPXBCPVUFRVBUJPO NPUJPO)FXSJUFTUIFNPOUIFCPBSE)FPSHBOJTFTUIFNJOUP UIFGPVS(BMJMFBOFRVBUJPOTPGNPUJPO U d = v BWH = (våOBM+ vinitial )/2 v BWH v instantaneousBtXJUIOPTUBSUJOHWFMPDJUZ 2 (with initial speed) d = vinitial t›Bt) v åOB2= vinitial 2 + 2ad (timeless) Grade 9 121 Grade 9: Physics syllabus Competencies Contents Suggested activities *Gvinitial UIFOFRVBUJPOCFDPNFTD = ½at 2BTXFIBWF BMSFBEZTFFO4UVEFOUTNBZBUUFNQUUPEFSJWFFRVBUJPO GSPNUIFPUIFST 1SPCMFNTPMWJOH"TJOUIFQSFWJPVTUFYUTUVEFOUTEPBM QSPCMFNTPMWJOHVTJOHUIFGPVS(BMJMFBOFRVBUJPOT 2RVBMJUBUJWFMZ Look at ½S = ut + at 5IFåSTUUFSNJTKVTUNPUJPOXJUIDPOTUBOUWFMPDJUZ 5IFBDDFMFSBUJPOUFSNIBTB›JOJU8IZ 1FFSJOTUSVDUJPO&RVBUJPOIBTB›JOJU "GPSUIFTBNFSFBTPOUIBUFRVBUJPOIBTB› #GPSBWFSZEJGGFSFOUSFBTPO Look at the area under a vWTt graph with starting at non[FSPv 5IJTJTUIFBSFBPGBSFDUBOHMFQMVTBUSJBOHMF 4VCTUJUVUJPOXJMMHFUUIFMBTUFRVBUJPO 4UVEFOUTXJMMEFWFMPQTLJMMJOTFMFDUJOHXIJDIPGUIF(B FRVBUJPOTUPFNQMPZJOTPMWJOHQSPCMFNT5IFZTIPVMEFY TLJMMJOBQQMZJOHSVMFTGPSTJHOJåDBOUEJHJUTJOTPMW QSPCMFNT "TLTUVEFOUTUPDBSSZPVUDBMDVMBUJPOTPOSFMFWBOUG t (VJEFTUVEFOUTJOJOWFTUJHBUJOHUIFWBMVFPGg in their MPDBMJUZVTJOHGSFFGBMMFYQFSJNFOU -FUTUVEFOUTQSPEVDFHSBQITPGVOJGPSNMZBDDFMFSBUF 5IFIVNBOMJOFIBTNVDINPSFBWBJMBCMFNBUFSJBM 5IJTJTBMMGVOEBNFOUBMMZEPOFJOUIFIVNBOMJOFTFHNFO 2VFTUJPO8IZEFUFSNJOFUIFBDDFMFSBUJPOPGHSBWJUZ 0,HPBIFBEXJUIJUCVUPOMZGPSBEFNPPGBDDVSBDZBOE FYQFSJNFOUBMNFUIPE "DUJWJUZ4UBUJPOUXPQFSTPOTBUUIFUPQBOECPUUPNPGB XBMMQSFGFSBCMZUXPTUPSJFTPSIJHIFS The person at the top should release a ball and the person at the bottom should measure the time taken to reach the HSPVOE5IFOVTFD = ½2UPEFUFSNJOFUIFWBMVFPGg gt t 6TFSFBMMJGFFYQFSJFODFPGUIFTUVEFOUTUPFYQMBJOU SFMBUJWFWFMPDJUZDPODFQUåSTUJOUIFTBNFEJSFDUJP UIFPQQPTJUFEJSFDUJPO .PEFMXJUI$IBOHFUIFEJSFDUJPOPGUIFTDBMFPGUIF)VNBO MJOF(P-FGUUPSJHIU8IBUEPFTUIBUEPUPUIFMJOFTPOUIF graphs? 122 Grade 9 Grade 9: Physics syllabus Competencies Contents Suggested activities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ssessment FUFBDIFSTIPVMEBTTFTTFBDITUVEFOUTXPSLDPOUJOVPVTMZPWFSUIFXIPMFVOJU BOEDPNQBSFJUXJUIUIFGPMMPXJOHEFTDSJQUJPOCBTFEPOUIFDPNQFUFODJFTUP EFUFSNJOFXIFUIFSUIFTUVEFOUIBTBDIJFWFEUIFNJOJNVNSFRVJSFEMFWFM Students at minimum requirement level "TUVEFOUXPSLJOHBUUIFNJOJNVNSFRVJSFNFOUMFWFMXJMMCFBCMFUPEFOFBOE EFTDSJCFDPODFQUTBOEVOJUTSFMBUFEUPNPUJPOFHWFDUPSTTDBMBSTEJTQMBDFNFOU VOJGPSNNPUJPOJOTUBOUBOFPVTBOEBWFSBHFWFMPDJUZVOJGPSNBDDFMFSBUJPO JOTUBOUBOFPVTBOEBWFSBHFBDDFMFSBUJPOEFTDSJCFBOEFYQMBJOEJFSFOULJOETPG NPUJPOBOEBQQMZRVBOUJUBUJWFMZSFMBUJPOTIJQTCFUXFFOEJTQMBDFNFOUWFMPDJUZ BDDFMFSBUJPOJOSFMFWBOUQSPCMFNTJOUFSQSFUQBUUFSOTBOEUSFOETJOEBUBCZNFBO PGHSBQITESBXOBOEJOGFSPSDBMDVMBUFMJOFBSBOEOPOMJOFBSSFMBUJPOTIJQTBNPOH 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t"QQSFDJBUFUIFWFDUPSOBUVSFPGGPSDFUIFBQQMJDBUJPOPG/FXUPOT MJGFBDUJWJUJFT Competencies Contents Suggested activities Students will be able 3. 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#FDBVTFPJMNBLFTUIJOHTTMJEF #FDBVTFPJMJTBSPVOENPMFDVMFBOEJUBDUTMJLFBCB CFBSJOH JTBUBVUPMPHZ 8IZEPFTHSFBTFNBLFUIJOHTTMJEF $MBTTSFTQPOTFCZHSP BGUFSNJOVUFEJTDVTTJPO*UJTNPSFTPMJEUIBOPJMBOE TNPPUIFTPVUUIFCVNQT 125 Grade 9: Physics syllabus Competencies Contents Students will be able to: t 6TFGSFFCPEZ diagrams SFQSFTFOUJOHGPSDFT POBCPEZUPTPMWF QSPCMFNT t 4UBUF/FXUPOTUIJSE MBX t (JWFFYBNQMFTXIFSF /FXUPOTUIJSEMBXJT BQQMJDBCMF t %FNPOTUSBUF /FXUPOTUIJSE MBXVTJOHJOýBUFE CBMMPPO t %FåOFUIFUFSN MJOFBSNPNFOUVN t &YQSFTTUIF dimension and unit PGNPNFOUVN t 4PMWFOVNFSJDBM problems using UIFEFåOJUJPOPG NPNFOUVN t 4UBUF/FXUPOT second law in terms PGUIFSBUFPGDIBOHF PGNPNFOUVN t 4UBUFUIFMBXPG DPOTFSWBUJPOPGMJOFBS NPNFOUVN t 6TFUIFMBXPG DPOTFSWBUJPOPGMJOFBS NPNFOUVNUPTPMWF SFMBUFEQSPCMFNT t &YQSFTTUIF dimension and unit PGJNQVMTF t %FTDSJCFUIF relationship between impulse and change JONPNFOUVN t 4PMWFQSPCMFNT VTJOHUIFJNQVMTFo momentum SFMBUJPOTIJQ t %JTUJOHVJTICFUXFFO elastic and inelastic DPMMJTJPO 126 Suggested activities 5FMMTUVEFOUTUIBUJOUIFQSFWJPVTMFTTPOTGSJDUJPOBM BTTVNFEUPCFOFHMJHJCMF#VUJOSFBMMJGFGSJDUJPOGPS [FSP t %PEFNPOTUSBUJPOUPEJTUJOHVJTICFUXFFOTUBUJDBOEL GSJDUJPO t6TJOHUIFFRVBUJPO F = µNEPTBNQMFRVFTUJPOT Calculate static µ GPSBUBCMFPSEFTL %PUIFTBNFGPSUIFTBNFCMPDLPOSPVHITBOEQBQFS Calculate kinetic µ GPSBUBCMFPSEFTL6TJOHUIFTBNFCMPDL 1VUTPNFPJMPSHSFBTFPOUIFTBOEQBQFSNBLFBQSFEJDUJP Calculate static µ with oil on the sandpaper -FUTUVEFOUTTBZTPNFUIJOHBCPVUIPXUIFZIBWFQMBZFEXJU DBSUNBEFGSPNXPPEBOECBMMCFBSJOH "TLTUVEFOUTUPHJWFSFBMMJGFFYBNQMFTPGBDUJPOBOES .BLFBMJTUPOUIFCPBSE8IJDIJTUIFBDUJPOXIJDIJTUIF reaction? )BWFTUVEFOUTNBLFESBXJOHT*GUIFSFJTNPUJPOIBWFUIF TUVEFOUTIPXXIJDIGPSDFDBVTFTUIFNPUJPO3FNFNCFSXJUI BCJLFPOUIFSPBEJUJTUIF30"%QVTIJOHCBDLUIBUDBVTFT UIFNPUJPO %FåOFGSFFCPEZEJBHSBN 'PSFBDIPGUIFTUVEFOUTVHHFTUJPOTUIFUFBDIFSESBXTBGS CPEZEJBHSBNPOUIFGPSDFT'#%T'SFFCPEZEJBHSBNTIFMQ GPDVTUIFNJOEPOUIFQIZTJDTPGBTJUVBUJPO *OWJUFNPSFTUVEFOUTVHHFTUJPOT*OWJUFBTUVEFOUUPE '#%BSPVOEUIFTJUVBUJPOT Peer instruction: 5IFJOTUSVDUPSQVUTVQTPNFESBXJOHTXJUIGPSDFTPOUIFN 4PNFBSFDPSSFDUTPNFBSFXSPOH *TUIJTBDPSSFDU'#% :FT /P "DUJWJUZ5XPTUVEFOUTPODIBJSTPQQPTFFBDIPUIFSBOEQV XJUIUIFJSMFHTPOUIFDIBJST8IBUBSFUIFGPSDFTPOUIF TZTUFN *OWJUFTUVEFOUTUPUFMM.BLFBEJBHSBN#FDMFBS BCPVUXIBUGPSDFJTPOXIBUPCKFDU*ODSFBTFUIFGPSDFVOU POFNPWF8IZEPFTUIFMJHIUFSPOFNPWF *TUIFGPSDFMFTT %PVCMFUIFXFJHIUPGUIFMJHIUPOFXJUIUXPTUVEFOUT%PJU BHBJO 3FESBXUIFEJBHSBNT *OWJUFTUVEFOUTUPHJWFJEFBTPGXIBUiNPNFOUVNwNFBOT UIFN Separate out non-physics usages: political momentum, NPNFOUVNJOBTPDDFSHBNFGPSBUFBN *NQPSUBOUiUIFGPSDFCFIJOEBNPWJOHPCKFDUUIBULFFQTJ NPWJOHwJTBGBMTFJEFB*UJTDBMMFEiJNQFUVTwQFPQMFU UIBUUIFUISPXFSHBWFBiNPUJPOGPSDFwUPBOPCKFDUUIBUL JUHPJOH Grade 9 Grade 9: Physics syllabus Competencies Contents Students will be able to: t "QQMZUIFåSTU DPOEJUJPOPG FRVJMJCSJVNUPTPMWF SFMBUFEQSPCMFNT t 4UBUFUIFDPOEJUJPO GPSMJOFBSFRVJMJCSJVN t +VEHFXIFUIFSB HJWFOTZTUFNJTJO FRVJMJCSJVNPSOPU Grade 9 Suggested activities /FXUPOHBWFBNVDICFUUFSTDJFOUJåDJEFB %FåOFUIFDPODFQUPGNPNFOUVN *UJTBWFDUPSRVBOUJUZP = mV 5IFBSSPXTJOEJDBUFUIFWFDUPSOBUVSFPGNPNFOUVNVTV denoted as P "DUJWJUZ2VBMJUBUJWFTFOTFPGNPNFOUVN Class work: 8IJDIIBTNPSFNPNFOUVN "LHCBMMNPWJOHBUNTPSBLHCBMMNPWJOHBUNT 0OFUIJOLTBCPVUIBWJOHBDPMMJTJPOXJUITPNFDMBZ8IJD NBLFTBCJHHFSEFOU 5IBUPOFIBTNPSFNPNFOUVN "LHCBMMNPWJOHBUNTPSBLHCBMMNPWJOHBUNTFD &YQMBJOUIFBOTXFS Peer instruction: 0CKFDUTIBWFNPNFOUVNPVUJOTQBDF :FT /P %JTDVTTJPO.PNFOUVNJTEFåOFEPONBTTOPUXFJHIU 0CKFDUTPVUJOTQBDFFWFOJOQMBDFTXJUIOPHSBWJUZXJ NPNFOUVN *NQPSUBOUQPJOU+VTUMJLFNBTTNPNFOUVNJTPOFPGUIF JNQPSUBOUVOJWFSTBMQSPQFSUJFTPGNBUUFS*UJTOPUB POFIPXFWFS &WFSCFFOIJUIBSECZBTPDDFSCBMM .BTTPGBTPDDFSCBMMHN 4QFFEPGBLHTPDDFSQMBZFSLN )PXGBTUNVTUBTPDDFSCBMMCFHPJOHGPSUIFHPBMJFUPG like he has been hit by a person? *TUIBUBSFBTPOBCMFTQFFEGPSBLJDLFSUPBUUBJOJOBTP kick? %PTPNFDBMDVMBUJPOT)PXMPOHEPFTBQPXFSGVMLJDLG HPBMJFTUBZJOUIFBJS )PXGBSEPFTJUHP $BMDVMBUFBNBYTQFFEPGBLJDL %PBOPUIFSDBMDVMBUJPO,OPXJOHUIFTQFFEPGBWFSZGB TPDDFSCBMMXIBUTQFFENVTUB,HTPDDFSQMBZFSIBWFUP BUUBJOUIFTBNFNPNFOUVN*TUIJTGBTUPSTMPX 8IBUDBOZPVTBZBCPVUUIFTQFFEPGBLHTPDDFSQMBZFS 8IBUTQFFEXPVMEIFIBWFUPHPUPIBWFUIBUNPNFOUVN 4PMWFTJNQMFFYBNQMFTPONPNFOUVN t (JWFBOFYFSDJTFPONPNFOUVNGPSUIFTUVEFOUTJOUIFD &RVBMNPNFOUVNVOFRVBMNPNFOUVN t/PDPOTFSWBUJPOZFU 127 Grade 9: Physics syllabus Competencies Contents Suggested activities 4PMWFTJNQMFFYBNQMFTPOJNQVMTFBOENPNFOUVN t (JWFBOFYFSDJTFPOJNQVMTFBOENPNFOUVNGPSUIFTUVEF JOUIFDMBTT*NQVMTFIBTBWFSZTQFDJåDNFBOJOHJOQIZTJ It does not mean anything like a mental idea or a will or a XJTI t 'PSDFJTXIBUDIBOHFTBOPCKFDUTWFMPDJUZ/FXUPOT to v2 which MBXTUFMMVTUIBUBDIBOHFJOWFMPDJUZGSPNv IBQQFOFEGSPNUIFBDUJPOPGUIFGPSDFf mv2omv p #VUUIBUDIBOHFJONPNFOUVNJTDBVTFECZBGPSDFBDUJOH PWFSUJNF$POTJEFSUIFVOJUT 'PSDFYUJNF/UNTFDUJNF/UNTFD 5IJTIBTUIFTBNFVOJUTBTNPNFOUVN 3FMBUJPOCFUXFFONPNFOUVNBOEJNQVMTF mV2omV P = Force × time 5IJTTJNQMFFRVBUJPOXJMMHJWFWFSZTVSQSJTJOHSFTVMU &YBNQMFTPOJNQVMTFBOENPNFOUVN t (JWFBOFYFSDJTFPOJNQVMTFBOENPNFOUVNGPSUIFTUVEF JOUIFDMBTT 8JUIUIFEFåOJUJPOPGNPNFOUVNDPNJOHGSPN/FXUPOT 6OJWFSTBMMBXTUIFSFJTBOFXDPOTFSWBUJPOMBXoUIF DPOTFSWBUJPOPGNPNFOUVN*UJTVOJWFSTBMBQQMZJOHG BUPNTUPHBMBYJFT0OFDBOOPUMPTFPSHBJONPNFOUVNVO BOZDPOEJUJPO pinitial = pnal r r Pinitial = Pnal 5IJTFRVBUJPOBQQMJFTJOJOEJWJEVBMDBTFTBTXFMMBTBD XIPMFVOJWFSTF .PNFOUVNJTDPOTFSWFEJOBMMDPMMJTJPOT "UåSTUXFXJMMDPOTJEFSTPNFLJOETPGJOFMBTUJDDPMMJT POFJOXIJDIUIFUXPPCKFDUTNFFUBOEGPSNPOFBGUFSUIF DPMMJTJPO %PTPNFFYBNQMFTPGJOFMBTUJDDPMMJTJPOT "LHTPDDFSHPBMJFKVNQTVQWFSUJDBMMZ)FDBUDIFTB HTPDDFSCBMMHPJOHBULNT5IFUXPNPWFCBDLXBSET at what speed? "HCVMMFUUSBWFMJOHBULNTIJUTBLHMPHPOB GSJDUJPOMFTTTVSGBDF*UFNCFETJUTFMGJOUIFXPPE "UXIBUTQFFEEPUIFUXPNPWFBOEJOXIBUEJSFDUJPO 8IBUXPVMEIBQQFOJGUIFNBTTPGUIFCVMMFUXFSFH "SPDLFUJOTQBDFUVSOTPOJUTNPUPSTGPST5IFLH SPDLFUJTBUSFTUBUåSTU5IFGPSDFPGJUTNPUPSJT/ 8IBUJTJUTåOBMTQFFE That same rocket puts a steel rope onto a 200 kg satellite XIJDIJTBUSFTUBGUFSUIFNPUPSTUPQT8IBUTQFFEUPUIF DPVQMFENBTTFTOPXNPWFXJUI 128 Grade 9 Grade 9: Physics syllabus Competencies Contents Suggested activities -FUUIFTUVEFOUTEPTJNQMFPOFEJNFOTJPOBMDPOTFSWBU momentum problems (totally inelastic collisions) and impulse QSPCMFNXJUIPVUGSJDUJPO Instructor works the problem on the board: 4VSQSJTJOHDBMDVMBUJPONFBTVSJOHUIFVOTFFO $POTJEFSUIFHCVMMFUBHBJO*UJTUSBWFMJOHBULNTIJUT B,HMPHPOBGSJDUJPOMFTTTVSGBDF*UFNCFETJUTFMGJO XPPEDNEFFQ8IBUJTUIFBWFSBHFGPSDFUIFCVMMFUFYFSU on the log? It sounds impossible to do but the impulse &RVBUJPOXJMMMFUZPVEPJU 5IFCVMMFUXFOUGSPNLNTFDUPBCPVU[FSPLNTFD *UTBWFSBHFTQFFEXBTLNTd = BWHU v 4PDN but we know vBWHLNTFD4PULN km = vBWHU LNTFDT5IBUJTUIFUJNFJUUBLFTUIFCVMMFUUPFOUFS UIFXPPEBOETUPQ #VUUIFJNQVMTFFRVBUJPOTBZT Ftmv) mv) = m(v G-vi LHBCPVULNT¦LNTTP FTmv) = 5 kg km/s F¦LHLNTT 2 F LHLNT 2 #VU/LHNT The F on bullet to stop it must be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on the ball? 5IFTFBSFNPSFEJGåDVMUQSPCMFNT4UVEFOUTTIPVMEEPT FMBTUJDDPMMJTJPOTJOXIJDIPOMZPOFWBSJBCMFUIFNBT PCKFDUCPVODJOHPGGJTVOLOPXO Grade 9 129 Grade 9: Physics syllabus Competencies Contents Suggested activities 4PDDFSFYBNQMFTBSFHPPE .PUJPOJNQVMTFKFPQBSEZ 5IJTSFWJFXTBMMUIFUFSNTBOEDBMDVMBUJPOTPGUIFVOJU $BSE/UNT"OTXFSXIBUJTNPNFOUVN /T"OTXFSXJUIJTBOJNQVMTFPG/BQQMJFEPWFST0S XIBUJTBOJNQVMTFPG/T Or (mvGomv i "OTXFSXIBUJTBOJNQVMTFPSDIBOHFJO NPNFOUVN 0STPNFTJNQMFOVNFSJDBMQSPCMFNTXJUIDPOTFSWBUJPO FOFSHZXIFSFPOFUFSNIBTBRVFTUJPONBSLJOJU Assessment FUFBDIFSTIPVMEBTTFTTFBDITUVEFOUTXPSLDPOUJOVPVTMZPWFSUIFXIPM BOEDPNQBSFJUXJUIUIFGPMMPXJOHEFTDSJQUJPOCBTFEPOUIFDPNQFUF EFUFSNJOFXIFUIFSUIFTUVEFOUIBTBDIJFWFEUIFNJOJNVNSFRVJSFEMFWF Students at minimum requirement level "TUVEFOUXPSLJOHBUUIFNJOJNVNSFRVJSFNFOUMFWFMXJMMCFBCMFUP BOEEFTDSJCFDPODFQUTBOEVOJUTSFMBUFEUPGPSDFBOENPUJPOFHWF BQQMJFEGPSDFOFUGPSDFTUBUJDGSJDUJPOLJOFUJDGSJDUJPODPFDJFO JEFOUJGZBOEEFTDSJCFUIFGVOEBNFOUBMGPSDFTPGOBUVSFBOBMZTFB UIFHSBWJUBUJPOBMGPSDFBDUJOHPOBOPCKFDUOFBSUIFTVSGBDFPGUI BOEEFTDSJCFUIFGPSDFTBDUJOHPOBOPCKFDUVTJOHGSFFCPEZEJBHSBN EFUFSNJOFUIFBDDFMFSBUJPOPGUIFPCKFDUTUBUF/FXUPOTMBXTBOEBQQ FYQMBJOUIFNPUJPOPGPCKFDUTJOBWBSJFUZPGDPOUFYUTBOBMZTFJOR VTJOH/FXUPOTMBXTUIFSFMBUJPOTIJQTBNPOHUIFOFUGPSDFBDUJOHPOB JUTNBTTBOEJUTBDDFMFSBUJPOBOBMZTFBOEFYQMBJOUIFSFMBUJPOTIJQ VOEFSTUBOEJOHPGGPSDFTBOENPUJPOVTFWFDUPSTUSJHPOPNFUSZBO PGWFDUPSTJOUPQFSQFOEJDVMBSDPNQPOFOUTUPEFUFSNJOFUIFOFUG PCKFDUBOEJUTSFTVMUJOHNPUJPOEFOFBOEEFTDSJCFUIFDPODFQUTBO UPNPNFOUVNJNQVMTF Students above minimum requirement level 4UVEFOUTXPSLJOHBCPWFUIFNJOJNVNSFRVJSFNFOUMFWFMTIPVMECFQS UIFJSBDIJFWFNFOUTSFDPHOJTFEFZTIPVMECFFODPVSBHFEUPDPOUJOVF IBSEBOEOPUCFDPNFDPNQMBDFOU Students below minimum requirement level 4UVEFOUTXPSLJOHCFMPXUIFNJOJNVNSFRVJSFNFOUMFWFMXJMMSFRVJS UIFZBSFUPDBUDIVQXJUISFTUPGUIFDMBTTFZTIPVMECFHJWFOFYUSBBUUF DMBTTBOEBEEJUJPOBMMFTTPOUJNFEVSJOHCSFBLTPSBUUIFFOEPGUIFE 130 Grade 9 Grade 9: Physics syllabus Unit 4: Work, energy and power (11 periods) Unit outcomes: Students will be able to: t%FWFMPQLOPXMFEHFBOEVOEFSTUBOEJOH PGNFDIBOJDBMXPSLFOFSHZBOE QPXFS t"DRVJSFLOPXMFEHFBOEVOEFSTUBOEJOHPODPMMJTJPOTJOPOFEJNFOTJPO t%FWFMPQTLJMMTJODPNQVUJOHUIFXPSLEPOFCZBGPSDFBQQMZJOHXPSLoFOFSHZ UIFPSFNBOEUIFMBXPGDPOTFSWBUJPOPGNFDIBOJDBMFOFSHZJOUIFTPMVUJPOPG QSPCMFNTBOEDPNQVUJOHNFDIBOJDBMQPXFS t%FWFMPQQPTJUJWFBUUJUVEFUPXBSETUIFXJTFVTFPGFOFSHZ Competencies Contents Suggested activities Students will be able 4.Work, energy and Class discussion: to: power *OWJUFTUVEFOUTUPTVHHFTUTPNFFYBNQMFTPGXPSL-JTU t %FTDSJCFUIF 4.1 Mechanical work XJUIPVUDPNNFOU5IFODBUFHPSJTFUIFNBTQIZTJDBMBOEO necessary conditions (2 periods) QIZTJDBMXPSL GPSXPSLUPCFEPOF t 8PSLEPOFCZB %FåOJUJPO8PSLJOHFOFSBMGPSDFEJTQMBDFNFOUDPTæ CZBGPSDF DPOTUBOUGPSDF %FåOJUJPO&OFSHZJTUIFDBQBDJUZUPEPXPSL8PSLBOE t %FTDSJCFUIFXPSL t 8PSLEPOFCZB FOFSHZIBWFUIFTBNFVOJUT5IFZBSFSFBMMZUIFTBNFRVBO EPOFCZBGPSDFF WBSJBCMFGPSDF CVUWJFXFEGSPNEJGGFSFOUQFSTQFDUJWFT acting on a body at 5IFSFBSFUXPLJOETPGFOFSHZLJOFUJDBOEQPUFOUJBM an angleæ to the 4.2 Work–energy $MBTTEFNPOTUSBUJPOTXJUITUVEFOUJOWPMWFNFOUPGE IPSJ[POUBM theorem (2 periods) BHBJOTUTFWFSBMEJGGFSFOUGPSDFT)BWFBTFUPGåWFB t 6TFW = FS cos æ TFUVQGPSVTFCZTUVEFOUQBJST5IFTFJODMVEFBTQSJOH UPTPMWFSFMBUFEt,JOFUJDFOFSHZ PTDJMMBUPSBCPYQVTIFEBDSPTTUIFýPPSBEPVCMFQVMMF t1PUFOUJBMFOFSHZ QSPCMFNT IBOHJOHGSPNBIPPLJOUIFDFJMJOHBSVCCFSCBOEXJUIB t.FDIBOJDBMFOFSHZ mass hanging (manipulated by the student), a large, slow t $BMDVMBUFUIFXPSL EPOFCZBGPSDFPG QFOEVMVN5IFQFOEVMVNBOETQSJOHTIPVMECFTFUJONPU HSBWJUZPOBCPEZ4.3 Conservation of &BDITUVEFOUIBWFMBSHFDBSETMBCFMFEi*ODSFBTJOH,&w t %JTUJOHVJTICFUXFFO UIFCBDLi*ODSFBTJOH1&w0OFCZPOFJOUIFEFNPOTUSBUJPO energy (6 periods) QPTJUJWFBOEOFHBUJWF UIFTUVEFOUTTIPVMEXJUIWPJDFBOEDBSETDPNNFOUPOUIF t 5IFMBXPG XPSL DPOTFSWBUJPOPGQSPDFTT4UBSUXJUIUIFQFOEVMVN4UVEFOUTFYQMBJOUIF DIPJDFTUPQQJOHUIFBQQBSBUVTJGOFFEFE*GBNJTUBLFJT t $BMDVMBUFUIFXPSLenergy NBEFBOPUIFSTUVEFOUUBLFTIJTPSIFSQMBDF5IFJOTUSVDU EPOFCZBGSJDUJPOBM t $PMMJTJPO4JOPOF BTLTi8IFSFJTBGPSDFNPWJOHBDSPTTBEJTUBODF w GPSDF dimension 8IFOTUVEFOUTBSFDPNGPSUBCMFMBCFMJOHUIFQSPDFTT t %FUFSNJOFUIFXPSL t &OFSHZJOBO EPOFCZBWBSJBCMF oscillating pendulum instructor increases the complexity by adding a card: “work EPOFCZHSBWJUZwPSi8PSLEPOFCZUIFTQSJOHw GPSDF t &OFSHZJOBTQSJOHo "OEi8PSLEPOFCZUIFQFSTPOwBMTPi8PSLEPOFCZUIFSVCCF t &YQMBJOUIF mass system CBOEwPSi8PSLEPOFCZUIFQFSTPOw relationship between XPSLBOEFOFSHZ $MBTTEFNPOTUSBUJPO"TQSJOHPTDJMMBUJOH,JOFUJDFO 4.4 Mechanical power CFDPNFTQPUFOUJBMBOEUIFOCFDPNFTLJOFUJD t %FSJWFUIF QFSJPE relationship between Peer instruction on kinetic and potential energy: t8JTFVTFPGFOFSHZ work and kinetic 1FOEVMVN8IFOJT1&UIFMBSHFTU FOFSHZ #PVODJOHCBMM8IFOJT,&UIFTNBMMFTU #BMMPOBSPQFWFSUJDBMMZ8IFOJT,&MBSHFTU 8IFOJT1&MBSHFTU #BMMPOBSPQFIPSJ[POUBMMZ8IFOJT,&MBSHFTU Grade 9 131 Grade 9: Physics syllabus Competencies Contents Students will be able to: t 4PMWFSFMBUFE problems using the relationship between work and kinetic FOFSHZ t 4IPXUIFSFMBUJPOTIJQ between work and potential energy as W = –U. t %FTDSJCFHSBWJUBUJPOBM QPUFOUJBMFOFSHZ t %FTDSJCFFMBTUJD QPUFOUJBMFOFSHZ t 4PMWFSFMBUFE problems using W = –U t &YQMBJOUIF mechanical energy BTUIFTVNPGLJOFUJD BOEQPUFOUJBMFOFSHZ t 4UBUFUIFMBXPG DPOTFSWBUJPOPG NFDIBOJDBMFOFSHZ t %FåOFUIFUFSN DPMMJTJPO t %JTUJOHVJTICFUXFFO elastic and inelastic DPMMJTJPO t 4PMWFQSPCMFNT JOWPMWJOHJOFMBTUJD collision in one dimension using the MBXPGDPOTFSWBUJPO PGNFDIBOJDBMFOFSHZ BOENPNFOUVN 132 Suggested activities "OTXFSJUJTBMXBZTUIFTBNFWFMPDJUZ5IJTJTSPUBUJPO8FM TUVEZUIBUMBUFS .BTTFTPOTQSJOHTXIFOJT,&1&MBSHFTU "8PSL&OFSHZ+FPQBSEZ .BUDIEFåOJUJPOTXJUIUIFUFSN*ODMVEFOVNFSJDBM DBMDVMBUJPOT$BSE/N"OTXFSXIBUJTUIFXPSLEPOFCZ B/GPSDFNPWJOHPOFNFUFS*ODMVEFGSJDUJPOUFSNTBMTP LHNTFD"OTXFSXIBUJTBLJOFUJDFOFSHZPGBLHNBTT NPWJOHBUNT (1&Mgh 'PSBTQSJOH1&›kd2 where kTQSJOHDPOTUBOU 'PSDFGPSBTQSJOHk x 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)PMEEJTDVTTJPOXJUIUIFTUVEFOUT 5FYU.PNFOUVNNVTUCFDPOTFSWFE5IFUPUBMFOFSHZNVTUC DPOTFSWFE5IFSFJTBTMJHIUQSPCMFNJOVTJOHUIFDPOTFSW PGFOFSHZUIFPSFNFWFSZXIFSF4PNFUJNFTFOFSHZJTiMPTUw JOUIFGPSNPGIFBUUISPVHIGSJDUJPO*UJTOPUSFBMMZMPTU NBEFJOWJTJCMFJOUIFNPMFDVMBSNPUJPOPGBUPNT8FTIBM BTTVNFOPMPTTPGFOFSHZUPIFBU Grade 9 Grade 9: Physics syllabus Competencies Contents Students will be able to: t &YQMBJOUIFFOFSHZ changes that take place in an PTDJMMBUJOHQFOEVMVN t &YQMBJOUIFFOFSHZ changes that takes place in an PTDJMMBUJOHTQSJOHo NBTTTZTUFN% t %FTJHOUIFQSPQFS VTBHFPGFOFSHZ TPVSDFT t %JTDVTTBTZTUFNPG VUJMJ[JOHFOFSHJFTMJLF wind energy, solar energy, geothermal FOFSHZNPSFFGåDJFOU GPSMPDBMVTF t 4UBUFTPNFSFOFXBCMF TPVSDFTPGFOFSHZ t &YQSFTTUIFGPSNVMB PGNFDIBOJDBMQPXFS JOUFSNTPGBWFSBHF WFMPDJUZ t 4PMWFQSPCMFNT JOWPMWJOHUIF EFåOJUJPOPGQPXFS t 4IPXUIBULXISJT BMTPBVOJUPGXPSL FOFSHZ Suggested activities 5FYUXFLOPXIPXUPTPMWFNPUJPOQSPCMFNTXJUIUIF (BMJMFBOFRVBUJPOT5IFSFJTBNVDITJNQMFSXBZUPEPUIBU 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5&95HFOFSBUJPOPGQPXFSJTWFSZJNQPSUBOUGPS&UIJPQJ IBWFOPUZFUEJTDVTTFEFMFDUSJDBMFOFSHZ*UJTBOPUIFSL FOFSHZUIBUJTBMTPDPOTFSWFE 134 Grade 9 Grade 9: Physics syllabus Competencies Contents Suggested activities &MFDUSJDBMFOFSHZJTHFOFSBUFEJOUXPXBZTGSPNTQJO BDPJMJOTJEFBNBHOFUJOBEZOBNPHFOFSBUPS5IFTFEZOB BSFQPXFSFEFJUIFSCZDPBMPJMGBMMJOHXBUFSXJOEQPX PSOVDMFBSFOFSHZJOUFSBDUJPOTBUUIFNPMFDVMBSMFW QIPUPWPMUBJDDFMMT*OUIFåSTUDBTFFOFSHZJTDPOWFS DIFNJDBMTPVSDFTJOUIFGVFMTNPWJOHFOFSHZLJOFUJDF PGXJOEPSXBUFSPSOVDMFBSFOFSHZGSPNTQMJUUJOHBU &UIJPQJBEFQFOETQSJNBSJMZPOIZESPQPXFS8IBUBSFUIF BEWBOUBHFTBOEMJNJUBUJPOTPGIZESPQPXFSBTUIFQPU TPVSDFPGFMFDUSJDBMFOFSHZ FH,JOFUJDFOFSHZoFMFDUSJDJUZ t1&JOUPLJOFUJDFOFSHZWJDFWFSTB t,JOFUJDFOFSHZoIFBUFUD #VJMEBDBSVTJOHSVCCFSCBOETBTQPXFSTPVSDFT5IFSFJ EFTJHOMJNJUPOFJUIFSOVNCFSPSLJOEPGXIFFMT FUD3VCCFSNFUBMEPVHIOVUTIBQFEPSDZMJOEFSTIBQFE5 cars will compete in a competition to see which one goes UIFGVSUIFTU5IFNBTTPGUIFDBSNVTUCFMFTTUIBOLH*U NVTUåUJOUPBCPYUIBUJTDNCZDNCZDN:PV NBZQJDLBOZNBUFSJBMTGPSUIFCPEZPSXIFFMT5IFEJTUBO USBWFMMFEXJMMCFNFBTVSFEPOBTUSBJHIUMJOFQFSQFO UPUIFTUBSUJOHQPJOU*GUIFDBSTQBUIJTDSPPLFEPOMZUI normal displacement component counts as distance Students NVTUTQFOETFWFSBMXFFLTXPSLJOHJOHSPVQTPOUIFJSDB 5IFZDBOOPUVTFQSFNBEFUPZDBST5IFZDBOCPSSPXQBSUT GSPNUIFNCVUOPUVTFXIPMFDBST5IFZNVTUEFDJEFIPXCFTU UPTUPSFUIFFOFSHZJOUIFTQSJOHBOEIPXCFTUUPUSBOTG UPUIFXIFFMT'SJDUJPOXJUIUIFSPBEJTJNQPSUBOU5PPNVDI TMPXTUIFDBSEPXO5PPMJUUMFDPOUBDUXJUIUIFSPBEBOE XIFFMTTQJO 5IFHSPVQNVTUQSFTFOUBSFQPSUJODMVEJOHBESBXJOHP car and explain their design decisions Grade 9 135 Grade 9: Physics syllabus Assessment FUFBDIFSTIPVMEBTTFTTFBDITUVEFOUTXPSLDPOUJOVPVTMZPWFSUIFXIPM BOEDPNQBSFJUXJUIUIFGPMMPXJOHEFTDSJQUJPOCBTFEPOUIFDPNQFUF EFUFSNJOFXIFUIFSUIFTUVEFOUIBTBDIJFWFEUIFNJOJNVNSFRVJSFEMFWF Students at minimum requirement level "TUVEFOUXPSLJOHBUUIFNJOJNVNSFRVJSFNFOUMFWFMXJMMCFBCMFUP BOEEFTDSJCFUIFDPODFQUTBOEVOJUTSFMBUFEUPFOFSHZXPSLBOEQPXF 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requirement level 4UVEFOUTXPSLJOHCFMPXUIFNJOJNVNSFRVJSFNFOUMFWFMXJMMSFRVJS UIFZBSFUPDBUDIVQXJUISFTUPGUIFDMBTTFZTIPVMECFHJWFOFYUSBBUUF DMBTTBOEBEEJUJPOBMMFTTPOUJNFEVSJOHCSFBLTPSBUUIFFOEPGUIFE 136 Grade 9 Grade 9: Physics syllabus Unit 5: Simple machines (11 periods) Unit outcomes: Students will be able to: t%FWFMPQLOPXMFEHFBOEVOEFSTUBOEJOHPGCBTJDQSJODJQMFTPGTJNQMFNBDIJOFT BOEQVSQPTFTPGNBDIJOFT t%FWFMPQNBOJQVMBUJWFTLJMMTJOVTJOHBOEIBOEMJOHTJNQMFNBDIJOFTBOE DPOTUSVDUJOHTJNQMFNBDIJOFT t%FWFMPQJOUFSFTUJOVTJOHTJNQMFNBDIJOFTUPEPXPSLJOEBJMZMJGFBDUJWJUJFT Competencies Contents Suggested activities Students will be able 5. 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PFluid statics 1SFTTVSFJTEFåOFEBTUIFBNPVOUPGGPSDFBQQMJFEQFSVO to: BSFB1SFTTVSFDBOCFNFBTVSFEXJUINBOZEJGGFSFOUVOJU 6.1 Air pressure 0OFPGUIFNPTUDPOGVTJOHBTQFDUTBCPVUQSFTTVSFJTUIF t %FåOFUIFUFSN (5 periods) XJEFWBSJFUZPGVOJUTVTFEUPNFBTVSFJU*UJTJNQPSUBOU QSFTTVSF t 5IFNBHOJUVEFPGBJS TUVEFOUTSFBMJTFBMMUIFTFVOJUTBSFTJNQMZEJGGFSFOU t 6TFUIFEFåOJUJPO pressure NFBTVSJOHUIFTBNFUIJOHOBNFMZUIFSBUJPPGGPSDFUPBSF PGQSFTTVSFUPTPMWF t "JSQSFTTVSFBOE "DUJWJUZ SFMBUFEQSPCMFNTbreathing "UNPTQIFSJDQSFTTVSFBUTFBMFWFMJT,1B*TUIJTBMBSHF t %FTDSJCFBUNPTQIFSJD QSFTTVSFPSBTNBMMPOF 5PVOEFSTUBOEUIFNBHOJUVEFPG QSFTTVSF 6.2 Fluid pressure atmospheric pressure, you must relate it to something with t &YQMBJOUIFWBSJBUJPO QFSJPET XIJDIZPVBSFGBNJMJBS:PVDBODPNQBSFBUNPTQIFSJDQSFTTVS PGBUNPTQIFSJD t4JQIPOT UPUIFQSFTTVSFZPVFYFSUPOUIFýPPS4JODFQSFTTVSFJTEFåO pressure with as p= F/A, you can calculate the pressure you exert on the t )PXEPFTXBUFS BMUJUVEF ýPPSJGZPVLOPXZPVSXFJHIUBOETVSGBDFBSFBPGDPOUBDU QSFTTVSFWBSZXJUI t &YQMBJOIPXUP .FBTVSFUIFDPOUBDUBSFBPGZPVSGFFU%SBXUIFPVUMJOFPG depth measure atmospheric ZPVSTIPFPOBQJFDFPGHSBQIQBQFSBOEDPVOUUIFOVNCFSPG t1BTDBMTQSJODJQMF QSFTTVSF TRVBSFTJOTJEFUIFåHVSF.VMUJQMZUIFOVNCFSPGTRVBSFTC t"SDIJNFEFTT t 4IPXUIBUN)H UIFBSFBPGBOJOEJWJEVBMTRVBSFTUPEFUFSNJOFUIFBQQSPY principle is equal to one TVSGBDFBSFBPGUIFCPUUPNPGZPVSGFFU4UVEFOUTBOTXFSN BUNPTQIFSFY WBSZEFQFOEJOHVQPOUIFJSXFJHIUBOEUIFTVSGBDFBSFBPGU 1B CPUUPNPGUIFJSGFFU*OHFOFSBMTUVEFOUTTIPVMEåOEUIBUB 5 QSFTTVSFJTBQQSPYJNBUFMZåWFUJNFTBTHSFBUBTUIFQSFTT t %FåOFUIFUFSNýVJE UIFZFYFSUPOUIFýPPSXIFOTUBOEJOHPOCPUIGFFU t 4UBUFUIFTJNJMBSJUJFT "DUJWJUZ BOEEJGGFSFODFT between liquids and 5PJOWFTUJHBUFIPXHSFBUBUNPTQIFSJDQSFTTVSFJTTUVEFOU HBTFT BMTPQFSGPSNUIFADPMMBQTJOHDBOFYQFSJNFOU5IFUSFNFO pressure exerted by air can be demonstrated in a dramatic t %FåOFUIFUFSNT GBTIJPOVTJOHUXPESBJOQMVOHFST8IFOUXPQMVOHFSTBSF EFOTJUZBOESFMBUJWF QSFTTFEUPHFUIFSUPGPSNBUJHIUTFBMJUCFDPNFTWFSZEJG EFOTJUZ UPQVMMUIFNBQBSU$PWFSUIFBEKPJOJOHTVSGBDFTPGUXP t %FUFSNJOFUIF QMVOHFSTXJUIMJHIUHSFBTFTPBHPPETFBMXJMMGPSNBOEQV EFOTJUZBOESFMBUJWF UIFNUPHFUIFS"TUIFQMVOHFSTDPMMBQTFBJSFTDBQFTBOEJGB EFOTJUZPGBCPEZJO HPPETFBMGPSNTOPBJSXJMMFOUFSXIFOQSFTTVSFJTSFMFBTF BHJWFOQSPCMFN 8IFOZPVTUPQQVTIJOHPOUIFQMVOHFSTUIFSVCCFSJOUIFIFBE t &YQMBJOIPXUIF PGUIFQMVOHFSXJMMFYQBOEEVFUPJOUFSOBMSFTUPSJOHGP pressure in a liquid UIFIFBETFYQBOEBQBSUJBMWBDVVNJTDSFBUFEDBVTJOHUIF BUSFTUWBSJFT GPSNBUJPOPGBQSFTTVSFEJGGFSFOUJBMCFUXFFOUIFPVUTJ UIFJOTJEFPGUIFQMVOHFST(PPVUTJEFUIFDMBTTBOEUSZUPQV UIFQMVOHFSTBQBSU$BOZPVEPJU 140 Grade 9 Grade 9: Physics syllabus Competencies Contents Students will be able to: t "QQMZUIFGPSNVMB p = ghUPTPMWF SFMBUFEQSPCMFNT t $BMDVMBUFUIFUPUBM pressure on a body JOTJEFBýVJEVTJOH UIFGPSNVMBP total = Patm + gh t 4UBUF1BTDBMT QSJODJQMF t 6TF1BTDBMT principle to explain UIFGVODUJPOPGB IZESBVMJDMJGUQSFTT t "QQMZ1BTDBMT QSJODJQMFUPTPMWF SFMBUFEQSPCMFNT t &YQMBJOUIFVTFPG NBOPNFUFS t %FNPOTUSBUF VOEFSTUBOEJOHPG atmospheric pressure, gauge pressure and BCTPMVUFQSFTTVSF t %JTUJOHVJTICFUXFFO absolute pressure and HBVHFQSFTTVSF t $BMDVMBUFUIF absolute and gauge QSFTTVSFPGBýVJEJO BDPOUBJOFS t 4UBUF"SDIJNFEFTT QSJODJQMF t %JTUJOHVJTICFUXFFO true weight and BQQBSFOUXFJHIUPGB CPEZ t $BMDVMBUFUIFCVPZBOU GPSDFBDUJOHPOB CPEZJOBýVJE Grade 9 Suggested activities $PODFQUTUPJOWFTUJHBUFNFBTVSJOHBUNPTQIFSJDQSF BOFSPJECBSPNFUFSXFBUIFSGPSFDBTUJOH "TJNQMFBOFSPJECBSPNFUFSDBOCFNBEFGSPNIPVTFIPME NBUFSJBMTBOEVTFEUPPCTFSWFDIBOHFTJOBJSQSFTTVSF BXJEFNPVUIFEFNQUZKBSBOETFBMJUXJUIBTIFFUPG.ZMBS .ZMBSJTVTFEJOBMVNJOJTFEQBSUZCBMMPPOTJTSFMBUJW impermeable to gas, and thereby allows balloons to remain JOýBUFENVDIMPOHFSUIBOCBMMPPOTNBEFPGSVCCFS4US BTIFFUPG.ZMBSVOUJMJUGPSNTBUJHIUESVNPWFSUIFUPQ PGUIFKBSBOEVTFIFBWZSVCCFSCBOETUPIPMEJUJOQMBDF 1MBDFBTNBMMQJFDFPGDIFXJOHHVNPSPUIFSBEIFTJWFJO DFOUSFPGUIFNFNCSBOFBOEBUUBDIUIFFOEPGBTQBHIFUU OPPEMFCSPPNTUSBXUPUIFHVN5IFOFFEMFDBOQJWPUPO UIFFEHFPGBKBS"TBUNPTQIFSJDQSFTTVSFEFDSFBTFTUIF QSFTTVSFJOTJEFUIFKBSXJMMFYDFFEUIFFYUFSOBMQSFTT 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JTUIFTBNFJOBMMEJSFDUJPOT*GGPSFYBNQMFBCBMMPPO submerged in water, it will assume a smaller spherical shape as water presses equally upon it in all directions, rather than BýBUUFOFETIBQFBTJGTPNFPOFTBUPOJU5IFBJSJOUIF submerged balloon transmits pressure equally in all directions TPUIFCBMMPPONBJOUBJOTBTQIFSJDBMTIBQF 1BTDBMTQSJODJQMFTUBUFTUIBUýVJETUSBOTNJUQSFTTV JOBMMEJSFDUJPOT 141 Grade 9: Physics syllabus Competencies Contents Students will be able to: t 4UBUFUIFQSJODJQMFPG ýPUBUJPO t &YQMBJOXIZCPEJFT ýPBUPSTJOL t $BMDVMBUFUIFEFOTJUZ PGBýPBUJOHCPEZ PSEFOTJUZPGBýVJE VTJOHýPUBUJPO QSJODJQMF 142 Suggested activities "DUJWJUZ$POTUSVDUB6UVCFCZCFOEJOHBTFDUJPOPGHMB UVCJOH"MUFSOBUJWFMZZPVNBZVTFUXPTUSBJHIUQJFDFTP HMBTTDPOOFDUFECZBOBSDPGýFYJCMFUVCJOH"EEXBUFSU UIF6UVCFVOUJMJUJTBQQSPYJNBUFMZIBMGGVMM.FBTVSFU IFJHIUPGUIFXBUFSJOCPUIBSNTBOESFDPSEJUJOBUBCMF 6TJOHBQBJSPGTDJTTPSTDVUBTFDUJPOGSPNBMBSHFCBMM FOPVHIUPåUPWFSUIFPQFOJOHPGBTNBMMGVOOFM4USFUD NBUFSJBMPWFSUIFPQFOJOHBOETFDVSFJUXJUISVCCFSCBO 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"SDIJNFEFTTUBUFEUIBUBOZPCKFDUTVCNFSHFEPSýPBUJOH BýVJEJTCVPZFEVQXBSECZBGPSDFFRVJWBMFOUUPUIFXFJH PGý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ýPXT0ODFXBUFSIBTTUPQQFEýPXJOHQMBDFBESZ HSBEVBUJOHDZMJOEFSPSPUIFSDPOUBJOFSCFOFBUIUIFTQP BCFBLFS)BOHUIFPCKFDUGSPNUIFTDBMFBOETMPXMZJNNFS JUJOUIFCFBLFSTVDIUIBUBMMPGUIFEJTQMBDFEXBUFSýPXT PWFSUIFTQPVUBOEJOUPUIFHSBEVBUJOHDZMJOEFS3FDPSE OFXXFJHIUPGUIFTVCNFSHFEPCKFDU5IFXFJHIUPGXBUFS displaced can be measured by collecting and weighing all UIFXBUFSUIBUPWFSýPXTGSPNUIFCFBLFS"OBMZTFUIFSFTVM SFDPSEFEJOUIFUBCMF*TUIFXFJHIUPGUIFEJTQMBDFEXBUFS FRVBMUPUIFEJGGFSFODFJOUIFXFJHIUPGUIFPCKFDUXIFO measured in air or in water? Grade 9 Grade 9: Physics syllabus Assessment FUFBDIFSTIPVMEBTTFTTFBDITUVEFOUTXPSLDPOUJOVPVTMZPWFSUIFXIPMFVOJU BOEDPNQBSFJUXJUIUIFGPMMPXJOHEFTDSJQUJPOCBTFEPOUIFDPNQFUFODJFTUP EFUFSNJOFXIFUIFSUIFTUVEFOUIBTBDIJFWFEUIFNJOJNVNSFRVJSFEMFWFM Students at minimum requirement level "TUVEFOUXPSLJOHBUUIFNJOJNVNSFRVJSFNFOUMFWFMXJMMCFBCMFUP EFOF BOEEFTDSJCFUIFDPODFQUTBOEVOJUTSFMBUFEUPVJETFHEFOTJUZBUNPTQIFSJD QSFTTVSFBCTPMVUFQSFTTVSFQSFTTVSFWPMVNFJEFOUJGZGBDUPSTBFDUJOHTUBUJD QSFTTVSFBOBMZTFTUBUJDQSFTTVSFJORVBOUJUBUJWFUFSNTBOEFYQMBJOJUTFFDUT JOMJRVJETBOEHBTFTTUBUF1BTDBMTQSJODJQMFBOEFYQMBJOJUTBQQMJDBUJPOTJOUIF USBOTNJTTJPOPGGPSDFTJOVJETZTUFNTTUBUF"SDIJNFEFTTQSJODJQMFBOEFYQMBJO JUTBQQMJDBUJPO Students above minimum requirement level 4UVEFOUTXPSLJOHBCPWFUIFNJOJNVNSFRVJSFNFOUMFWFMTIPVMECFQSBJTFEBOE UIFJSBDIJFWFNFOUTSFDPHOJTFEFZTIPVMECFFODPVSBHFEUPDPOUJOVFXPSLJOH IBSEBOEOPUCFDPNFDPNQMBDFOU Students below minimum requirement level 4UVEFOUTXPSLJOHCFMPXUIFNJOJNVNSFRVJSFNFOUMFWFMXJMMSFRVJSFFYUSBIFMQJG UIFZBSFUPDBUDIVQXJUISFTUPGUIFDMBTTFZTIPVMECFHJWFOFYUSBBUUFOUJPOJO DMBTTBOEBEEJUJPOBMMFTTPOUJNFEVSJOHCSFBLTPSBUUIFFOEPGUIFEBZ Grade 9 143 Grade 9: Physics syllabus Unit 7: Temperature and heat (12 periods) Unit outcomes: Students will be able to: t%FWFMPQLOPXMFEHFBOEVOEFSTUBOEJOHPGUFNQFSBUVSFIFBUUIFS FYQBOTJPOPGTVCTUBODFTRVBOUJUZPGIFBUBOEDIBOHFPGTUBUF t%FWFMPQTLJMMTJODPNQVUJOHUIFBNPVOUPGIFBUTQFDJDDBQBDJUZ IFBUBOEUIFSNBMFYQBOTJPOPGNBUFSJBMT t"QQSFDJBUFUIFJNQPSUBODFPGUIFIJHIWBMVFPGTQFDJDIFBUDBQBDJU BCOPSNBMFYQBOTJPOPGXBUFS Competencies Contents Suggested activities Students will be able 7. Temperature and %FNP to: heat .BUFSJBMTTPMJESVCCFSCBMM%SJMMBIPMFJOUPJUUIBUXJ t &YQMBJOUIFEJGGFSFODF 7.1 Temperature and åUBUIFSNPNFUFS%SJMMBTFDPOEIPMFXJUIBNVDIUIJOOFS between heat and heat (2 periods) drill so that a thin but strong wire can go through, like a UFNQFSBUVSF QBQFSDMJQ1VUUIFXJSFPSQBQFSDMJQUISPVHIBOECFOEPW t)FBUBOEUFNQFSBUVSF POFFOETPJUDBOOPUDPNFPVU"UUBDIBUPVHITFUPGSVCCFS t %FåOFUIFUFSN t5IFSNBMFYQBOTJPO bands to the wire, and then attach that to a board shaped UIFSNBMFRVJMJCSJVN t )FBUBTNPMFDVMBSMJLFBUFOOJTSBDLFU5IFCBMMTIPVMECPVODFPGGJUFBTJM t %FTDSJCFUIFUIFSNBM motion .BLFUIFMFOHUIPGUIFSVCCFSCBOETBCPVUNFUSF5BLF FYQBOTJPOPGTPMJET t 'JSTUMBXPG UIFUFNQFSBUVSFPGUIFCBMM*OWJUFBTUVEFOUUPDPNFVQ t %FSJWFUIFFYQSFTTJPO thermodynamics QPVOEUIFCBMMPGGUIFýPPSNJHIUJMZ GPSMJOFBSFYQBOTJPO t 4FDPOEMBXPG *HOPSFUIFTUVEFOUXIJMFZPVJOWJUFUIFDMBTTUPTIBSFJEF PGTPMJET thermodynamics BCPVUIFBUFOFSHZ8IBUJTJU t %FSJWFUIFFYQSFTTJPO RVBMJUBUJWF *TJUBýVJE *TIFBUBUIJOH GPSTVSGBDFBSFBM treatment) #FUIFBUSJDJGUIFTUVEFOUTUPQTQPVOEJOHSFNJOEIJNPGIJ FYQBOTJPOPGTPMJET KPC$POUJOVFQPMMJOHUIFTUVEFOUTGPSJEFBTPGIFBU$PV t 'JOEUIFSFMBUJPOTIJQ 7.2 Expansion of CFBýVJEJOTJEFTVCTUBODF 8IZBOEXIZOPU CFUXFFODPFGåDJFOU solids, liquids and 3FNJOEUIFTUVEFOUUPLFFQQPVOEJOH PGMJOFBSBSFBBOE gases QFSJPET WPMVNFFYQBOTJPO "GUFSBCPVUNJOVUFTUBLFUIFUFNQFSBUVSFPGUIFCBMM t .FOUJPOBQQMJDBUJPOT 8IZEJEJUHPVQ 7.3 Quantity of heat, PGUIFSNBMFYQBOTJPO *OWJUFBOTXFST$PVMEIFBUCFBýVJEGSPNUIJTFYQFSJNFOU specic heat capacity PGNBUFSJBMT $PNNPOMBOHVBHFUSFBUTIFBUBTTPNFUIJOHUIBUýPXTGSPN and heat capacity (bimetallic strip, BåSFPSBIPUUJQPGNFUBMUPBDPMEFSFOE4UVEFOUTTIPVME QFSJPET thermostat) BQQSFDJBUFUIBUIFBUJTOPUBTVCTUBODFJUJTWJCSBUJPO t 4PMWFQSPCMFNT t )FBUFYDIBOHF BUPNTPSNPMFDVMFTJOUIFTVCTUBODF JOWPMWJOHMJOFBS(calorimetery) BSFBBOEWPMVNF FYQBOTJPOPGTPMJET 7.4 Changes of state QFSJPET t %JTUJOHVJTICFUXFFO apparent and real t-BUFOUIFBU FYQBOTJPOPGBMJRVJE t 4PMWFQSPCMFNT JOWPMWJOHFYQBOTJPO PGMJRVJETVTJOHUIF GPSNVMB V oT= V t &YQMBJOUIFBCOPSNBM FYQBOTJPOPGXBUFS 144 Grade 9 Grade 9: Physics syllabus Competencies Contents Students will be able to: t $PNQBSFUIF FYQBOTJPOPGHBTFT XJUIFYQBOTJPOPG TPMJETBOEMJRVJET t %FåOFUIFUFSNT TQFDJåDIFBUDBQBDJUZ BOEIFBUDBQBDJUZPG BCPEZ t %FTDSJCFUIFGBDUPST UIBUBGGFDUUIF BNPVOUPGIFBU absorbed or liberated CZBCPEZ t *EFOUJGZEJGGFSFOU VOJUTPGIFBUFOFSHZ t $BMDVMBUFUIF RVBOUJUZPGIFBU absorbed or liberated by a body using the GPSNVMBQ = mDT t $BMDVMBUFUIFIFBU DBQBDJUZPGBCPEZ t &YQMBJOUIF TJHOJåDBODFPGIJHI TQFDJåDIFBUDBQBDJUZ PGXBUFS t 4PMWFQSPCMFNT JOWPMWJOHIFBU exchange using the relationship heat lost IFBUHBJOFE t %FTDSJCFUIFVTFTPG BDBMPSJNFUFS t %FåOFUIFUFSN latent heat t %FåOFUIFUFSNT MBUFOUIFBUPGGVTJPO BOEMBUFOUIFBUPG WBQPSJTBUJPO t 4PMWFQSPCMFNT JOWPMWJOHDIBOHFPG TUBUF Grade 9 Suggested activities 5FYU5IFUFBDIFSCSJOHTPVUBiNBHJDXBOEwIFDMBJNTDBO iUBMLUPBUPNTw*UJTBSJEJDVMPVTTUJDLXJUIGFBUIFSTCF BOEDPMPVSFEQBQFS)FQVUTUIFIFBUFECBMMPOBUBCMFB IPMETUIFTUJDLOFBSUIFCBMMBOEUIFQBEEMFPOUPQPGUIF TUJDLi*XBOUBMMPGZPVBUPNTJOTJEFUPTUBSUNPWJOHJO TBNFEJSFDUJPOVQBOEEPXOBOETUBSUCPVODJOHw/PUIJO IBQQFOTIFNPWFTUPBOPUIFSUBCMFBOEBTLTTUVEFOUTUP IFMQ 8IZDBOOPUBMMUIFBUPNTEFDJEFUPNPWFJOPOFEJSFDUJP upwards and then start bouncing again? *OWJUFTUVEFOUSFTQPOTFT Students should appreciate that heat is totally random motion PGBUPNTBOENPMFDVMFT5IFNPUJPODBOOPUCFSFPSEFSF UPTPNFUIJOHMJLFLJOFUJDFOFSHZPGBCPEZ)FBUJTNPUJP FOFSHZBUBOBUPNJDBOENPMFDVMBSMFWFM5IFSFJTOPXB DPOWFSUUIBULJOEPGNPUJPOJOUPTPNFUIJOHFMTFMJLFL FOFSHZ 5IJTJTUIFTFDPOEMBXPGUIFSNPEZOBNJDT*UMJLF/FXUPOT MBXTBOEUIFDPOTFSWBUJPOMBXTJTPOFPGUIFHSFBUVOJ QSJODJQMFT3BOEPNNPUJPODBOOPUCFVOEPOF*UBMTPN UIBUUJNFIBTBEJSFDUJPOTPNFQSPDFTTFTDBOOPUCFSFW 4UVEFOUTBMSFBEZLOPXUIFåSTUMBXJUJTUIFDPOTFSWBU FOFSHZ )BWFBTIFFUPGNFUBMXJUIBIPMFJOJUBOEBCBMMUIBUåUT SJHIUJOXIFODPME*GUIFTIFFUJTIFBUFEXJMMUIFCBMMBMT in? %FNPOTUSBUJPO"CPMUBOEOVUåUXFMMUPHFUIFS)FBUUIF XJMMUIFCPMUåUJO 8IZ %FNPOTUSBUJPO)BWFBCBMMPPOUFUIFSFEBUBJSUFNQFS .FBTVSFJUTDJSDVNGFSFODF)PMEJUPWFSBDBOEMFýBNFB TVGåDJFOUEJTUBODFOPUUPJOKVSFUIFSVCCFSGPSBGFX UPIFBUUIFBJS.FBTVSFUIFEJBNFUFSPGUIFCBMMPPO %JTDVTTUIFCBTJDLJOFUJDUIFPSZPGNBUUFSXJUITUVEFOU RVBMJUBUJWFMZ t 4UBUFUIFFGGFDUPGUFNQFSBUVSFPOUIFNPUJPOPGQBS RVBMJUBUJWFMZ t3FDBQJUVMBUFUIFFGGFDUTPGIFBUJOHBCPEZ t %FNPOTUSBUFFYQBOTJPOPGTPMJETMJRVJETBOEHBTFT 1SFTFOUBUJPO4IPXUIFHSBQIPGUIFIFBUOFFEFEUPSBJTF HSBNPGXBUFSGSPN¦°$UP°$ %FNPTUBSUXBUFSIFBUJOHJOTPNFDPOUBJOFS6TFFMFDUS PSBOBMDPIPMMBNQ6TFBTNBMMBNPVOU8IFOJUJTCPJMJO LFFQSFBEJOHUIFUFNQFSBUVSF 8IZJTJUOPUJODSFBTJOH )FBUJTHPJOHJO 5FYUJOUSPEVDFTMBUFOUIFBUPGWBQPSJTBUJPOKH,TGPS XBUFS 145 Grade 9: Physics syllabus Competencies Contents Suggested activities *OUSPEVDFMBUFOUIFBUPGNFMUJOHGVTJPOGPSXB (SPVQXPSLoBTTFTTNFOUBTTJHOFBDIHSPVQPGo TUVEFOUTBTQFDJåDBNPVOUPGXBUFSJOBKBSPSDV .BLFJUSBOHFGSPNHUPLH)PXNVDIIFBUXJMM JUUBLFUPHFUUIBUBNPVOUPGXBUFSUP°C? Assessment FUFBDIFSTIPVMEBTTFTTFBDITUVEFOUTXPSLDPOUJOVPVTMZPWFSUIFXIPM BOEDPNQBSFJUXJUIUIFGPMMPXJOHEFTDSJQUJPOCBTFEPOUIFDPNQFUF EFUFSNJOFXIFUIFSUIFTUVEFOUIBTBDIJFWFEUIFNJOJNVNSFRVJSFEMFWF Students at minimum requirement level "TUVEFOUXPSLJOHBUUIFNJOJNVNSFRVJSFNFOUMFWFMXJMMCFBCMFUP UFSNTUIFSNBMFRVJMJCSJVNUIFSNBMFYQBOTJPOTDIBOHFPGQIBTFDBMP TQFDJDIFBUDBQBDJUZMBUFOUIFBUPGWBQPSJTBUJPOMBUFOUIFBUPGGV UIFVOJUTGPSUIFUFSNTIFBUIFBUDBQBDJUZTQFDJDIFBUDBQBDJUZMBUFO UIFSFMBUJPOTIJQCFUXFFOIFBUUSBOTGFSSFEBOEPCTFSWFEDIBOHFJOU TPMWFQSPCMFNTJOWPMWJOHDBMDVMBUJPOTPGIFBUMPTUIFBUHBJOFE FYQBOTJPOPGNBUFSJBMT Students above minimum requirement level 4UVEFOUTXPSLJOHBCPWFUIFNJOJNVNSFRVJSFNFOUMFWFMTIPVMECFQS UIFJSBDIJFWFNFOUTSFDPHOJTFEFZTIPVMECFFODPVSBHFEUPDPOUJOVF IBSEBOEOPUCFDPNFDPNQMBDFOU Students below minimum requirement level 4UVEFOUTXPSLJOHCFMPXUIFNJOJNVNSFRVJSFNFOUMFWFMXJMMSFRVJS UIFZBSFUPDBUDIVQXJUISFTUPGUIFDMBTTFZTIPVMECFHJWFOFYUSBBUUF DMBTTBOEBEEJUJPOBMMFTTPOUJNFEVSJOHCSFBLTPSBUUIFFOEPGUIFE 146 Grade 9 Grade 9: Physics syllabus Unit 8: Wave motion and sound (16 periods) Unit outcomes: Students will be able to: t%FWFMPQLOPXMFEHFBOEVOEFSTUBOEJOHPGXBWFTUZQFTPGXBWFTQFSJPEJD NPUJPOXBWFNPUJPODIBSBDUFSJTUJDTPGXBWFTBOEQSPQFSUJFTPGXBWFT t%FWFMPQLOPXMFEHFBOEVOEFSTUBOEJOHPGTPVOEXBWFTQSPQFSUJFTPGTPVOE XBWFTBOEDIBSBDUFSJTUJDTPGTPVOE t%FWFMPQTLJMMTJODPNQVUJOHUIFTQFFEQFSJPEGSFRVFODZPGBXBWFJOUIF TPMVUJPOPGQSPCMFNT t%FWFMPQTLJMMTJODPNQVUJOHUIFJOUFOTJUZPGTPVOEXBWFT t"QQSFDJBUFUIFBQQMJDBUJPOPGSFFDUJPOPGTPVOEXBWFBOEUIFSPMFPGXBWFTJO UFDIOPMPHZ Competencies Contents Suggested activities Students will be able 8.Wave motion and *OWJUFTUVEFOUTUIPVHIUTPOUIFNFBOJOHPGBQIZTJDBM to: sound XBWF8IFSFEPZPVTFFUIFN 8IBUUZQFTBSFUIFSF *OWJUF t %FåOFUIFUFSNT 8.1 Wave propagation TUVEFOUTSFTQPOTFT-JTUUIFN XBWFBOEXBWFQVMTF QFSJPET 6TFBMBSHFUSBZUPEFNPOTUSBUFXBWFTJOXBUFS t %FåOFUIFUFSNT t 1VMTFBOEUSBJOPG 6TFBSPQFUPEFNPOTUSBUFXBWFT crest, trough, XBWF $MBTTSPPNMBCPSBUPSZUIFIVNBOXBWF XBWFMFOHUI t 5ZQFTPGXBWFT -BCTJNVMBUJPO4USFUDIUIFTMJOLZEPXOPOFSPXPG BNQMJUVEFGSFRVFODZ mechanical and TUVEFOUT6TFNPSFUIBOPOFTMJOLZUBQFEUPHFUIFSJGOF BOEQFSJPEPGBXBWF electromagnetic 4UVEFOUTBSFNPEFMTGPSNPMFDVMFTPGXBUFS.BLFBSJQ t 4PMWFQSPCMFNT XBWFT POFFOEPGUIFTMJOLZ5IFZXJMMTJNVMBUFUIFNPUJPOPGBX JOWPMWJOH JOUIFXBUFS.PEFMUIFNPUJPOPGBXBWFEPXOUIFTMJOLZ XBWFMFOHUI 8.2 Mechanical waves QPXFSFECZTUVEFOUTTFWFSBMUJNFT GSFRVFODZBOEXBWF QFSJPET -BCTJNVMBUJPO#SJOHJOBCBTLFUCBMM.PWFUPBOPUIFS TQFFE SPXPGTUVEFOUT(PUPUIFNJEEMFPGUIFDMBTTBOEiESPQw t $IBSBDUFSJTUJDTPG t %JTUJOHVJTICFUXFFO UIFCBTLFUCBMMJOUPUIFFOEPGUIFiXBUFSwTJNVMBUFECZ XBWFT NFDIBOJDBMXBWFT TMJOLZ4UVEFOUTJNJUBUFNPUJPOXJUIUIFTMJOLZBTJGJUX and electromagnetic t8BWFFRVBUJPOT UIFNPUJPOPGUIFXBUFSXBWFT"UUIFFOEUIFZHPEPXOBOE t 5SBOTWFSTFBOE UIFOVQBOEUIFXJHHMFNPWFTEPXOUIFTMJOLZUPUIFFOEPG XBWF MPOHJUVEJOBMXBWFT t *EFOUJGZUSBOTWFSTF UIFSPX and longitudinal -BCTJNVMBUJPO#SJOHJOUIFJEFBPGUJNF"EEBOFXSVMF XBWFTJOB 8.3 Properties of 6TFTPNFUJNJOHEFWJDFUIBUNBLFTBTPVOEFWFSZTFDPOE mechanical media waves QFSJPET FWFSZTFDPOET*UDPVMECFBMPOHQFOEVMVN5IFSVMFJTU (string, spring, water, UPQPGUIFXBWFNVTUNPWFBUFYBDUMZPOFEFTLFWFSZCF TFJTNJD PGUIFQFOEVMVNFWFSZPOFPSQSFGFSBCMZUXPTFDPOET 8.4 Sound waves t *EFOUJGZUIBU UFBDIFSTUBSUTUIFXBWFBUUIFGSPOUFOEOPUJOUIFNJEEM QFSJPET BTPVOEXBWFJT 5IJTSPXPGTUVEFOUTQSBDUJDFTNBLJOHUIFXBWFNPWFXJ t 1SPEVDUJPOBOE a longitudinal FYBDUMZUIJTTQFFEoPOFEFTLFWFSZTFDPOE*GUIFSFBSFT QSPQBHBUJPOPGTPVOE NFDIBOJDBMXBWF SPXTJUXJMMUBLFBCPVUTFWFOTFDPOETGPSUIFXBWFUPH t 4QFFEPGTPVOEJO UPUIFCBDL4UVEFOUTNPEFMUIJTTQFFEPGUIFXBWFTFWFS t &YQMBJOBCPVUUIF EJGGFSFOUNFEJB UJNFT0OFXBWFPOMZNPWFTEPXOUIFSPX QSPEVDUJPOPGTPVOE t4QFFEPGTPVOEJOBJS t %FTDSJCFIPXTPVOE t3FýFDUJPOPGTPVOE is propagated in a NBUFSJBMNFEJVN t "QQMJDBUJPOPG SFýFDUJPOPGTPVOE t $IBSBDUFSJTUJDTPG sound Grade 9 147 Grade 9: Physics syllabus Competencies Contents Students will be able to: t %FåOFUIFUFSNT compression and SBSFGBDUJPO t $PNQBSFUIFTQFFE PGTPVOEJOTPMJET MJRVJETBOEHBTFT t %FUFSNJOFUIFTQFFE PGTPVOEJOBJSBUBOZ HJWFOUFNQFSBUVSF t %FåOFUIFUFSN JOUFOTJUZPGBTPVOE t 4PMWFQSPCMFNT JOWPMWJOHJOUFOTJUZ PGTPVOEVTJOHUIF GPSNVMB*QPXFS BSFB t &YQMBJOUIFFGGFDUPG SFGSBDUJPOPGTPVOE t &YQMBJOUIFEJGGFSFODF between echo and SFWFSCFSBUJPO t %FTDSJCFTPNF BQQMJDBUJPOTPG SFýFDUJPOPGTPVOE t %FTDSJCFUIF characteristics PGTPVOEQJUDI MPVEOFTTRVBMJUZ t %FåOFUIFUFSNT EJGGSBDUJPOBOE JOUFSGFSFODF t %FTDSJCFUIF characteristic QSPQFSUJFTPGXBWFT SFýFDUJPOSFGSBDUJPO EJGGSBDUJPOBOE JOUFSGFSFODF 148 Suggested activities -BCTJNVMBUJPO5IFUFBDIFSTUPQTUIFXBWFBOEEFåOFT UXPOFXJEFBToTQFFEBOESFýFDUJPO5IFMBTUTUVEFOUBDU MJLFUIFXBWFCPVODFEPGGUIFXBMM"TUIFXBWFNPWFTEPXO the row then back to the start position, teacher asks the PUIFSSPXTi8IBUFYBDUMZJTUIFUJNFJUUBLFTUIFXBWFUP NPWFGSPNUIFGSPOUUPUIFCBDLUIFOUPUIFGSPOUBHBJO 5IFSVMFJTUIBUUIFUPQPGUIFXBWFNVTUNPWFBUPOFEFTL QFSQFOEVMVNIJU4UVEFOUTUJNFUIFXBWF5IFZNFBTVSFUIF EJTUBODFCFUXFFOUIFNJEEMFPGUIFEFTLT5IFZDBMDVMBUF TQFFEJONFUSFTQFSTFDPOE -BCTJNVMBUJPO6TJOHBCSJEHJOHNFUBQIPSJEFBUIF 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SFTFSWFEGPSGPSDF*UTGSFRVFODZJT cycle f= sec %FåOJUJPO8BWFMFOHUIJTUIFQIZTJDBMEJTUBODFGSPNPO PGBDZDMFUPUIFPUIFS5IFTZNCPMGPSXBWFMFOHUIJTUIF (SFFLMFUUFSMBNCEB $PMMFDUUIFTMJOLZ i8IBUJTUIFTQFFEJONFUSFTTFDPGPVSIVNBOXBWF i*OWJUFTUVEFOUTUPTVHHFTUBOEEFGFOEUIFJSJEFBTPGXI UIFTQFFEPGUIFXBWFJTNFBTVSFEJOUIFPCKFDUTPGUIFJS DMBTTSPPN*UJTUIFEJTUBODFUSBWFMMFEJOPOFDZDMFPG XBWF5IJTJTUIFEJTUBODFCFUXFFOUXPEFTLTBCPVUPOF NFUSFPSBCJUMFTT4UVEFOUTNFBTVSFUIFEJTUBODFCFUXF EFTLTBCPVUNFUSF4PXSJUJOHPOUIFCPBSEXFIBWF 4QFFEPGUIFXBWFEJTUBODFQFBLoQFBLQFSJPE 4QFFEPGUIFXBWFQFSJPE Grade 9 Grade 9: Physics syllabus Competencies Contents Suggested activities #VUQFSJPEGSFRVFODZ so f speed = = × f =f f f f 3FXSJUJOHUIJTFRVBUJPOOFBUMZXFHFUTQFFE = f 5IJTJTPOFPGUIFHSFBUFRVBUJPOTPGQIZTJDT*UJTOPUBMB SBUIFSJUJTJOUIFGPSNPGBEFåOJUJPOBTGSFRVFODZDZDM BOEEJTUBODFBOETQFFEBSFBMMLOPXORVBOUJUJFT *OUIFDBTFPGMJHIUBTQFDJBMTZNCPMJTVTFE5IFMFUUFST NT JTSFTFSWFEGPSUIFTQFFEPGMJHIUNT× 5IFTVCTUJUVUJPOWBMJEPOMZGPSMJHIUJTc = f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he equation is: v = gd 5IJTFRVBUJPOJTOPUBHSFBUMBXPGQIZTJDT*UJTEFSJWFE CZBOBMZTJTVTJOH/FXUPOJBOQSJODJQMFTBOEBQQMJFT MJNJUFEDBTFPGXBUFSXBWFT*UTIPVMEOPUCFNFNPSJTFE "DUJWJUZ2VBMJUBUJWFMPPLJOHBUUIFFRVBUJPOv = gd *OTUVEFOUHSPVQTNBLFQSFEJDUJPOTBCPVUUIFSFMBUJW PGXBUFSXBWFTJOEFFQPDFBOTJOTNBMMQPOETPSSJWFS BQPPMPSUIJOMBZFSTJOBQMBUF 5IFJOTUSVDUPSDPMMFDUTJEFBTGSPNHSPVQTBCPVUXIBU 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EPBOPUIFSTJNVMBUJPOPGBiUFOOJTCBMMwXBWF %FåOJUJPO5IFBNQMJUVEFPGBXBWFJTUIFEJGGFSFODFJO height between the middle point and the highest or lowest QPJOU*UJTBNFBTVSFPGUIFFOFSHZJOUIFXBWF "DUJWJUZEJTDVTTJPO%JTDVTTXIBUIBTIBQQFOFEXJUIUIF iIBOEXBWFTw8IJDIXBZEJEUIFXBWFNPWF %JEUIF JOEJWJEVBMQBSUJDMFTPGUIFTUVEFOUTIBOETNPWF *GiZF which way? 8IBUEPFTPTDJMMBUJPOIBWFUPEPXJUIUIJT 4UVEFOUTTIPVMEVOEFSTUBOEUIBUUIFNPUJPOPGUIFXBUFS NPMFDVMFTJTBMXBZTBCPVUPOFDFOUSFQPJOU5IFZNPMFD PTDJMMBUFUIFZEPOPUNPWFXJUIUIFXBWFTEJSFDUJPO5IF XBWFJTBWJCSBUJPOUIBUNPWFTBDSPTTUIFXBUFSJOBEJSF QFSQFOEJDVMBSUPUIFNPUJPOPGFBDIPGUIFXBUFSNPMFDV 8BUFSXBWFTDBODBSSZUSFNFOEPVTQPXFSJOUTVOBNJTDB CZFBSUIRVBLFTVOEFSTFB"UTFBUIFUTVOBNJDBOCF NoNIJHI"QQSPBDIJOHMBOEUIFXBWFTCPUUPN ESBHTPOUIFPDFBOýPPS*UDBVTFTUIFXBWFUPQFBL 5TVOBNJTDBOCFBUPNIJHIIJUUJOHMBOE ,JOETPGUSBOTWFSTFXBWFT 8BUFSTVSGBDFXBWFTJOFBSUIRVBLFTUIFHSPVOEXJHHMFTV BOEEPXOGSPNBXBWFJOUIFFBSUIBOEMJHIU $MBTTEFNPOTUSBUJPOMPOHJUVEJOBMXBWFT 6TJOHUIFTBNFTFUVQPGUIFTMJOLZXJUITUVEFOUTBTUIF NFEJVNEFNPOTUSBUFBDPNQSFTTJPOXBWF 5IFJOTUSVDUPSCSJOHTUPHFUIFSBNTFHNFOUPGUIFTMJOLZ *USFCPVOET5IFTUVEFOUTIPMEJOHUIFTMJOLZSFQSFTFOUJO UIFNFEJVNPTDJMMBUFIPSJ[POUBMMZBCPVUJUTQPTJUJPO5 XBWFQSPDFFETBXBZGSPNUIFJOJUJBMQPJOUCZDPNQSFTT UIFTBNFEJSFDUJPOBTJUTNPUJPO4UVEFOUTNPWFBTFSJFTP DPNQSFTTJPOTEPXOUIFTMJOLZBUBDPOTUBOUTQFFE 5IJTXBWFJTIBSEFSUPNPEFM*UJTOPURVJUFBTWJTJCMFBTU USBOTWFSTFXBWF "TLTUVEFOUTXIBUUIFZUIJOLUIFXBWFMFOHUIPGB DPNQSFTTJPOXBWFNJHIUCF *UJTUIFEJTUBODFCFUXFFO DPNQSFTTJPOT *OWJUFTUVEFOUTUPUIJOLPGXIBUUIFQFSJPEPGBMPOHJUVE XBWFNJHIUCFJUJTUIFUJNFCFUXFFOBSSJWBMTPGB DPNQSFTTJPO 150 Grade 9 Grade 9: Physics syllabus Competencies Contents Suggested activities $PMMFDUUIFTMJOLZ $MBTTSPPNEFNPOTUSBUJPO-POHJUVEJOBMXBWFT 6TFBSPXPGTUVEFOUTUIBUEJEOPUQBSUJDJQBUF%POPUV BTMJOLZ"TLTUVEFOUTUPUXJTUUPTJUTJEFXBZTBCJU1VUP IBOETTPUIFZUPVDI5IFZTIPVMELFFQBSNTTUJGG1VTIUIF åSTUPOF8BUDIUIFDPNQSFTTJPOHPEPXOUIFSPX *OWJUFUIFMBTUTUVEFOUUPQVUIJTIBOEPOUIFXBMM8IFOIF HFUTDPNQSFTTFEBOENPWFTUPXBSEUIFXBMM/FXUPOTUIJ 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Students must appreciate that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ýBTIBOEUIFTPVO .BLFBMBSHFTUSJOHJOUPUIFGPSNPGBNVTJDBMJOTUSVNF 5JHIUFOJUBOEQMVDLJU-JTUFOUPUIFTPVOE*OWJUFTUVEF UPHVFTTXIBUJUTXBWFMFOHUINJHIUCF *UTXBWFMFOHUIJTUXJDFUIFMFOHUIPGUIFTUSJOH6TJOHU XBWFFRVBUJPODBMDVMBUFUIFGSFRVFODZPGUIFTPVOE #SJOHJOTPNFTUSJOHJOTUSVNFOUT6TFUIFXBWFFRVBUJP DBMDVMBUFUIFGSFRVFODZPGMPXQJUDIFTBOEPGIJHIQJU %FåOFTQFDUSVN*UJTBDPMMFDUJPOPGBMMQPTTJCMFGS 8JUITPVOEUIJTNFBOTBMMQPTTJCMFQJUDIFTGSPNWFSZM WFSZIJHI *OWJUFTUVEFOUTUPTIBSFLOPXMFEHFBCPVUGSFRVFODJF TPVOEUIBUIVNBOTDBOIFBSBOEQFSIBQTBCPVUGSFRVFOD BOJNBMTDBOIFBS&MFQIBOUTDBOIFBSFYUSFNFMZMPX GSFRVFODJFT5IFZDPNNVOJDBUFPWFSNJMFTXJUITPVOEIV DBOOPUIFBS%PHTIFBSWFSZIJHIGSFRVFODJFTIVNBOTDBO #BUTIFBSFYUSFNFMZIJHIGSFRVFODJFTVQUPDZDMFT TFDPOE 5IFVOJUDZDMFTQFSTFDPOEJTDBMMFEUIFIFSU[BCCSFWJB Grade 9 151 Grade 9: Physics syllabus Competencies Contents Suggested activities $MBTTSPPNEFNPOTUSBUJPO*OWJUFBSPXPGTUVEFOUTUPN BMPOHJUVEJOBMXBWFVTJOHUIFIVNBOXBWFNPEFM4UBSUU XBWFXJUIPOF )PXJTJUSFýFDUFEPGGUIFXBMMJOUIFCBDL %PBRVJDL RVBOUJUBUJWFDBMDVMBUJPOPGUIFTQFFEPGUIFiIVNBO MPOHJUVEJOBMXBWFw8IBUJTJUTTQFFEJGZPVLOPXUIFEJTU JONFUSFTGSPOUUPCBDLBOEUIFOUPGSPOUBHBJO *OWJUFTUVEFOUTUPUIJOLPGBXBZUIFZDPVMENFBTVSFUIF TQFFEPGTPVOEPVUTJEF (SPVQBDUJWJUZ'JOEBTQPUXJUIBCJHSFýFDUJOHXBMM.PWF BSPVOEUJMMZPVDBOIFBSBOFDIP.BLFBTIBSQOPJTFMJLF DMBQQJOHXPPEUPHFUIFS.PWFBSPVOEBOEVTFBTFDPOEIBO POBXBUDIUJMMZPVHFUBOFDIPCBDLJOPOFTFDPOE8IBUJT ZPVSDBMDVMBUJPOGPSUIFTQFFEPGTPVOE #SJOHJUCBDLU DMBTTSPPN.BLFBQMPUPGBMMNFBTVSFNFOUT5IFSFTIPVME TFWFSBMEP[FOTPGUIFN*TUIFTFUPGNFBTVSFNFOUTBDDVSB *TUIFBDDFQUFEWBMVFJOUIFSBOHFUIFDMBTTIBTNFBTVSFE there systematic error? How big is it? .BLFBIVNBOXBWFJOBOPUIFSSPX%POPUVTFBTMJOLZ Students twist 90°BOEDPOOFDUCZIPMEJOHIBOETPSGPSFBSN 5IFJOTUSVDUPSNBLFTBIPSJ[POUBMXJHHMFPOPOFFOE4UVE NPEFMUIFXBWFNPWJOHEPXOUIFSPX5IFTUVEFOUBUUIFFOE IPMETPOUPUIFXBMM)FNVTUMFBOCBDLBTUIFXBWFIJUTBOE UIFOMFBOGPSXBSEBTIFSFUVSOTUPWFSUJDBM5IFUSBOTWF XBWFOPXDPNFTCBDLUPUIFGSPOU %JTDVTTJPO)PXJTUIJTEJGGFSFOUGSPNUIFDPNQSFTTJPOX Or is it the same? 3FGSBDUJPOJTNPTUJNQPSUBOUDPNNFSDJBMMZXJUIMJHIU XFMMNPEFMJUUIFSF-JHIUUSBWFMTTMPXFSJOEFOTFSNFEJV Glass or water are denser than air, so light is slower in these NFEJB%JBNPOETBSFWFSZEFOTF-JHIUUSBWFMTWFSZTMPXM EJBNPOET 1FFSJOTUSVDUJPOPO8BWFT 'JOETPNFFYBNQMFT $POåSNVOEFSTUBOEJOH Classroom assessments 8BWFKFPQBSEZ .BLFTPNFDBSET 8IBUJTBUTVOBNJ "OTXFS)VHFPDFBOXBWF 8IBUJTUIFTQFFEPGBUTVOBNJ LNI 8IBUJTUIFXBWFFRVBUJPO Speed = f 8IBUJTSFGSBDUJPO %JBHSBNTMJLFDPNJOHJOUPBEFOTFSNFEJVN $PNJOHPVUPGBEFOTFSNFEJVNEJBHSBN 152 Grade 9 Grade 9: Physics syllabus Competencies Contents Suggested activities 4JNQMFOVNFSJDBMQSPCMFNTXJUIUIFXBWFFRVBUJPO 8IBUJTUIFTQFFEPGTPVOE NT 8IBUJTUIFTQFFEPGMJHIU m/s Y #PBSEFYQFSJNFOU "MMXBWFTNPWFPVUXBSEGSPNUIFTPVSDFJOBMMEJSFDUJ 5IFZEJTTJQBUFPGGJOUPTQBDFVOUJMBCTPSCFECZTPNF TVCTUBODF$POTJEFSUIFSBUFBUXIJDIJUEJTTJQBUFT Model with a rope and a chalk how sound, light or water get XFBLFSNPWJOHBXBZGSPNUIFTPVSDF Assessment FUFBDIFSTIPVMEBTTFTTFBDITUVEFOUTXPSLDPOUJOVPVTMZPWFSUIFXIPMFVOJU BOEDPNQBSFJUXJUIUIFGPMMPXJOHEFTDSJQUJPOCBTFEPOUIFDPNQFUFODJFTUP EFUFSNJOFXIFUIFSUIFTUVEFOUIBTBDIJFWFEUIFNJOJNVNSFRVJSFEMFWFM Students at minimum requirement level "TUVEFOUXPSLJOHBUUIFNJOJNVNSFRVJSFNFOUMFWFMXJMMCFBCMFUPEFOFBOE EFTDSJCFUIFDPODFQUTBOEVOJUTSFMBUFEUPNFDIBOJDBMXBWFTFHMPOHJUVEJOBM XBWFUSBOTWFSTFXBWFDZDMFQFSJPEGSFRVFODZBNQMJUVEFXBWFMFOHUI WFMPDJUZTVQFSQPTJUJPOEFTDSJCFBOEJMMVTUSBUFUIFQSPQFSUJFTPGUSBOTWFSTFBO MPOHJUVEJOBMXBWFTJOEJFSFOUNFEJBBOEBOBMZTFUIFWFMPDJUZPGXBWFTUSBWFMMJO JOUIPTFNFEJBJORVBMJUBUJWFUFSNTDPNQBSFUIFTQFFEPGTPVOEJOEJFSFOU NFEJBBOEEFTDSJCFUIFFFDUPGUFNQFSBUVSFPOUIFTQFFEPGTPVOEESBXBOBMZTF BOEJOUFSQSFUUIFQSPQFSUJFTPGXBWFTFHSFFDUJPOSFGSBDUJPOEJSBDUJPO JOUFSGFSFODFEVSJOHUIFJSUSBOTNJTTJPOJOBNFEJVNBOEGSPNPOFNFEJVNUP BOPUIFSBOEEVSJOHUIFJSJOUFSBDUJPOXJUINBUUFS Students above minimum requirement level 4UVEFOUTXPSLJOHBCPWFUIFNJOJNVNSFRVJSFNFOUMFWFMTIPVMECFQSBJTFEBOE UIFJSBDIJFWFNFOUTSFDPHOJTFEFZTIPVMECFFODPVSBHFEUPDPOUJOVFXPSLJOH IBSEBOEOPUCFDPNFDPNQMBDFOU Students below minimum requirement level 4UVEFOUTXPSLJOHCFMPXUIFNJOJNVNSFRVJSFNFOUMFWFMXJMMSFRVJSFFYUSBIFMQJG UIFZBSFUPDBUDIVQXJUISFTUPGUIFDMBTTFZTIPVMECFHJWFOFYUSBBUUFOUJPOJO DMBTTBOEBEEJUJPOBMMFTTPOUJNFEVSJOHCSFBLTPSBUUIFFOEPGUIFEBZ Grade 9 153 Physics Teacher Guide Grade 9 Author: Chris Sherry Graham Bone Susan Gardner Advisers: Tilahun Tesfaye Deressu (PhD) Endeshaw Bekele Buli Evaluators: Yosef Mihiret Gebremeskel Gebreegziabher Yusuf Mohamed Federal Democratic Republic of Ethiopia Ministry of Education