Acknowledgments
The development, printing and distribution of this teacher guide has been funded through the General Education
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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
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First edition, 2002 (E.C.)
ISBN: 978-99944-2-017-9
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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:
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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
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Class: Grade 9
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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
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NJOVUFT
Teaching and learning
activities
Introduce velocity–time
graphs and ask students
to work with a partner to
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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
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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
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illustrating.
Evaluation
Students should begin to
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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:
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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.
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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
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9 periods of
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Learning competencies
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2 periods of
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v %FGJOFUIFUFSNWFDUPS
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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.
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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
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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.
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5 periods of
Learning competencies
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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.
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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
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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.
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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
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Pythagoras’s theorem and vectors
SA
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MA
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CA
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Non-parallel and non-perpendicular vectors
SA
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Resolving vectors (1)
SA
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Resolving vectors (2)
SA
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MA
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CA
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Activities
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Grade 9
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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).
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2 periods of
Learning competencies
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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
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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:
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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
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Resources
http://www.physicsclassroom.com/class/vectors/u313c.cfm
Grade 9
21
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SA = starter activity MA = main activity CA = concluding activity
Combining vectors
SA
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MA
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Investigating vectors
SA
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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
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By the end of this unit students should be able to:
12 periods of
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Learning Competencies for Unit 2
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Learning Competencies
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Grade 9
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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
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Activity 2.2: Answer
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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
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Average and instantaneous speed and velocity
SA
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Activities
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Resources
http://www.physicsclassroom.com/class/idkin/u1l1d.cfm
Where next?
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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
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2 periods of
Learning Competencies
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Starting off
is section builds on the correct description of velocity to develop the students’
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and its units.
Teaching notes
Begin by asking the students what they understand by the term acceleration. Most
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It is important to note that acceleration is a change in velocity not a change in
speed. A change in velocity might be:
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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
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line), accelerating at constant speed (as they go round the bends) and decreasing
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Students should practise some acceleration calculations, including determining
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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
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CA
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Acceleration calculations
SA
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TQFFEBOEUJNFUIFTVCKFDUPGUIFFRVBUJPO
MA
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UIFJSPXOQSPCMFNTGPSBQBSUOFSUPTPMWFUIFZNVTUPGDPVSTFXPSLPVUUIFBOTX
UIFZDBODIFDLJU
CA
3FWJFXRVFTUJPOT¦%SBXHSBQIUPTIPXNPUJPOPGDBSJORVFTUJPOWFMPDJUZ¦UJNF
BOELFFQGPSOFYUMFTTPO
Activities
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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
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#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
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TIPXJOHBTFSJFTPG $POTUBOUWFMPDJUZ
lines and be able
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$POTUBOUWFMPDJUZTMPXFSUIBOHSBQIUIFOTUPQTUIFOUIFTBNFDPOTU
in relation to their
velocity as graph 1.
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4. Accelerating from rest.
DPNNFOUTTVDIBT
$POTUBOUWFMPDJUZUIFTBNFBTHSBQIUIFOHSBEVBMMZTMPXJOHEPXOU
XBMLJOHBUDPOTUBOU
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IPVTFXBJUJOHGPS start at the same velocity.
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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
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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:
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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
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MA
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CA
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BOEUIFOGFFECBDLJEFBTUPSFTUPGDMBTT
Velocitytime graphs
SA
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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?
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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
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4 periods of
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Starting off
is section builds on an understanding of what is meant by uniform acceleration
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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
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for vGSPNJOUP
s›uuatt
s›uatt
2
s›utat
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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
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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
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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
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MA
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CA
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Using the equations
SA
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CA
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Velocitytime graphs
SA
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EFSJWFs = ut›at 2
MA
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Free fall
SA
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MA
"DUJWJUZ
CA
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Activities
Activity 2.6: Answer
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s,
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BOE
u, v, a, t are known.
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ground. Emphasise that repeated readings improve the reliability of results.
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Use the results to calculate the acceleration due to gravity.
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Resources
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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.
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2 periods of
Learning Competencies
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Activity 2.7: Answers
Starting off
is section introduces the idea of a frame of reference. When we describe a
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moving object, we usually describe it from our own point of view. is is known
of:
as our frame of reference.
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LNI
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Teaching notes
oLNI
Begin by asking the students to point to the right. ey will all point to their
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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
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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
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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.
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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
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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
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By the end of this unit students should be able to:
19 periods of
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BT
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Learning Competencies for Unit 3
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t "QQMZ/FXUPOTTFDPOEMBXnet
BT=FmaUPTPMWFQSPCMFNT
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TJUVBUJPOT
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'PSDFTJOOBUVSF
Learning Competencies
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2 periods of
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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:
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Activity 3.2: Answer
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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
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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
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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.
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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
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Hooke’s law
SA
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Activities
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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
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Learning Competencies
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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
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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
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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.
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Grade 9
41
6OJU'PSDFBOE/FXUPOTMBXTPGNPUJPO
SA = starter activity MA = main activity CA = concluding activity
Forces and acceleration
SA
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Acceleration calculations
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UPHFUIFSXJUIBOPUIFSQBJSUPQPPMJEFBTCFGPSFGFFEJOHCBDLUPSFTUPGDMBTT
3FWJFXRVFTUJPO Activities
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situations.
= ma to solve problems.
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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.
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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
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Starting off
is section introduces the concept of friction as a force that opposes motion.
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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
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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.
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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
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inclined planes.
SA = starter activity MA = main activity CA = concluding activity
Causes and types of friction
SA
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MA
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Factors affecting frictional force
SA
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Reducing friction and the effects of friction
SA
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CA
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44
Grade 9
6OJU'PSDFBOE/FXUPOTMBXTPGNPUJPO
Activities
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friction.
t6TFUIFFRVBUJPOF = N to measure coecient of friction between various
surfaces.
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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
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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
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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!
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pushes the bottle up into the air.
Activity 3.5: Answer
Both students
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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
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Newton’s pair forces
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Applications of the third law (2)
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46
Grade 9
6OJU'PSDFBOE/FXUPOTMBXTPGNPUJPO
Activities
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push over a wall.
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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
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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
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TIPVME
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3 periods of
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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
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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
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the same magnitude of momentum but in opposite directions. e two players
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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,
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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
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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
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PSBNPVTFJGUIFZBSFCPUINPWJOHBUUIFTBNFTQFFE 8IZ
MA
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CA
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The law of conservation of linear momentum
SA
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MA
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CA
3FWJFXRVFTUJPOT¦
Momentum and Newton’s laws
SA
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IPXJUJTSFMBUFEUPNPNFOUVN
MA
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CA
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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
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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
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IJUTBOPUIFSCBMMPSUIFTJEFPGUIFUBCMF
MA
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CA
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Inelastic collisions
SA
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DPOTFSWFE 8IBUJTSFEVDFE
MA
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CPVODFCBDL
CA
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BOEPUIFSTQSFGFSBOBSUJGJDJBMTVSGBDF
Activities
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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
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#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
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JEFBT
MA
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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
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By the end of this unit students should be able to:
11 periods of
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the horizontal).
t 6TFW = F s cos to solve problems.
t $BMDVMBUFUIFXPSLEPOFBHBJOTUHSBWJUZUIFXPSLEPOFCZBGSJDUJ
BOEUIFXPSLEPOFCZBWBSJBCMFGPSDF
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t &YQMBJOUIFSFMBUJPOTIJQCFUXFFOXPSLBOEFOFSHZ
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solve problems.
t 4IPXUIFSFMBUJPOTIJQCFUXFFOXPSLBOEQPUFOUJBMFOFSHZBTW = U
use this to solve problems.
t %FTDSJCFHSBWJUBUJPOBMQPUFOUJBMFOFSHZBOEFMBTUJDQPUFOU
t &YQMBJONFDIBOJDBMFOFSHZBTUIFTVNPGLJOFUJDBOEQPUFOUJBMFO
t 4UBUFUIFMBXPGDPOTFSWBUJPOPGNFDIBOJDBMFOFSHZ
t 3FWJTFUIFUFSNDPMMJTJPOBOEEJTUJOHVJTICFUXFFOFMBTUJDBOEJO
DPMMJTJPOT
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BOEBOPTDJMMBUJOHTQSJOHoNBTTTZTUFN
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BOEHFPUIFSNBMFOFSHZ
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t 4PMWFQSPCMFNTSFMBUJOHUPUIFEFGJOJUJPOPGQPXFS
t 4IPXUIBUUIFL8IJTBMTPBVOJUPGXPSL
t &YQSFTTUIFGPSNVMBPGNFDIBOJDBMQPXFSJOUFSNTPGBWFSBHFWFM
54
Grade 9
6OJU8PSLFOFSHZBOEQPXFS
.FDIBOJDBMXPSL
Learning Competencies
5IJTTFDUJPO
TIPVME
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2 periods of
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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:
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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
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EFGJOJUJPOVTFEJOQIZTJDTUIBUQIZTJDBMXPSLNFBOTNPWJOHTPNFUIJOH
MA
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CA
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CFJOHEPOFCZPSBHBJOTUHSBWJUZFUDTFFQBHF
Calculating work
SA
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MA
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CA
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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
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2 periods of
solve problems.
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use this to solve problems.
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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.
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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
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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
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TIPVMECFNHPGPSBOHFXIJDIXJMMQSPWJEF+PGFOFSHZ"TLTUVEFOUTUPEFDJEFXIJD
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MA
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Potential energy
SA
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MA
CA
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TNBMMHSPVQT
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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
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6 periods of
Learning Competencies
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t 4UBUFUIFMBXPGDPOTFSWBUJPOPGNFDIBOJDBMFOFSHZ
Activity 4.6: Answer
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The football starts
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as it falls it loses
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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
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Teaching notes
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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
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ask for the device that performs those changes. Examples might include:
NPNFOUVNLH
tMBNQFMFDUSJDBM¤ light (but a lot of energy is “lost” as heat)
NTLJOFUJDFOFSHZ
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+
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
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= ½mAvA + ½mBvB
=½==+
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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
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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
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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
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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
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so much hydroelectricity and not coal, for example?
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SA = starter activity MA = main activity CA = concluding activity
Law of conservation of energy
SA
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MA
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Elastic and inelastic collisions
SA
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NBZDIBOHFJOFBDIDBTF
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CA
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Grade 9
61
6OJU8PSLFOFSHZBOEQPXFS
Energy in oscillating systems
SA
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CA
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¦
Energy resources
SA
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MA
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CA
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Renewable energy
SA
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ideas.
MA
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Energy in Ethiopia
SA
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MA
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CFOFGJUTBOEDPTUTGPSTVDIHFOFSBUJPOGPS&UIJPQJB
CA
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Activities
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kinetic energy and mass, linear momentum and velocity, linear momentum
and mass.
t#VJMEBUPZDBSVTJOHFMBTUJDCBOETBTUIFFOFSHZTPVSDF
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collisions.
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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
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1 period of
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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
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MA
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Activities
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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
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By the end of this unit students should be able to:
11 periods of
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Learning Competencies
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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
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with the load in the middle and class 3 with the eort in the middle
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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
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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.
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Introduce the terms mechanical advantage and velocity ratio. Stress that because
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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
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MA
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Activities
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mechanical advantage and ideal mechanical advantage are the same.
68
Grade 9
6OJU4JNQMFNBDIJOFT
Resources
http://www.mikids.com/5machines.htm
Where next?
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EFSJWJOHTQFDJDFYQSFTTJPOTGPSDBMDVMBUJOHUIF."BOE73GPSFBDI
Answers to review questions
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input is eort = distance moved by eort; work output is load = distance
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B+
C+
D
E
F
G
4. MA 9; load /
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Learning Competencies
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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
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Uses of air pressure (1)
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Uses of air pressure (2)
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Activities
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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.
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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
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Learning Competencies
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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
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81
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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.
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Activity 6.8: Answer
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results
Activity 6.9: Answer
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results
Activity 6.10:
Answer
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Discuss the main dierence between a gas and
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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.
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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
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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?
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Pressure in fluids
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Pascal’s principle
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Hydraulic machines
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Measuring pressure
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Forces in fluids
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Floating and sinking
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Activities
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containers either from given data or from the student’s own measurements.
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acts equally in all directions.
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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
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Learning Competencies for Unit 7
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By the end of this unit students should be able to:
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86
Grade 9
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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
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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
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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
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The laws of thermodynamics
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Activities
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from the Kelvin scale to Celsius.
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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
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Learning Competencies
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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
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Applications of thermal expansion
SA
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MA
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Expansion of liquids and gases
SA
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Activities
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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
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Learning Competencies
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UIFBNPVOUPGIFBUFOFSHZBCTPSCFEPSMJCFSBUFECZBCPEZVTJOH
Q = mc∆T
t $BMDVMBUFUIFIFBUDBQBDJUZPGBCPEZ
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IFBUFYDIBOHF
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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
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+LH,
Activity 7.8: Answer
ID+,UIF
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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
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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
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Finding the specific heat capacity of a substance
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What is the heat capacity of a body?
SA
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Activities
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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
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4 periods of
Learning Competencies
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t %FGJOFUIFUFSNTMBUFOUIFBUMBUFOUIFBUPGGVTJPOBOEMBUFOUIFB
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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
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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
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MA
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BNPVOUTPGTBMUBEEFEBTJUDPPMTBOEQMPUBDPPMJOHDVSWF
CA
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Specific latent heat (1)
SA
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MA
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Specific latent heat (2)
SA
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MA
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The specific latent heat of fusion of ice
SA
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MA
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CA
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Activities
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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:
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Unit 8
This unit should
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UIFZBSFQSPEVDFEBOEIPXUIFZQSPQBHBUF
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BQQMJDBUJPOT
8BWFQSPQBHBUJPO
Learning Competencies
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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
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results
Activity 8.2: Answer
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results
Activity 8.3: Answer
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results
Activity 8.4: Answer
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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.
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shoulder to shoulder with their arms linked. e student at the end moves from
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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.
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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
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fork gently against the ball. Although the vibration is too small to be visible with
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vibration from a large loudspeaker.
Provide examples of longitudinal waves to include:
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SA = starter activity MA = main activity CA = concluding activity
What are waves?
SA
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MA
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Longitudinal and transverse waves
SA
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MA
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Activities
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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
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be identied to allow the wave to be fully described.
Grade 9
99
6OJU8BWFNPUJPOBOETPVOE
Answers to review questions
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QMBDFUPBOPUIFSQVMTFoTJOHMFEJTQMBDFNFOUUIBUUSBOTGFSTFO
place to another
2. particles vibrate about a rest position
3. particle vibration at right angles to wave direction; water, light, radio,
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wave
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Learning Competencies
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Starting off
is section builds on the descriptions of transverse and longitudinal waves by
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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.
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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
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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.
&BSUIRVBLFXBWFTDBODBVTFNBTTJWFEFTUSVDUJPOPGQSPQFSUZBOETFSJPVTMPTTPG
MJGF&BSUIRVBLFTTUBSUJOTJEFUIF&BSUIXIFOUXPPGUIFUFDUPOJDQMBUFTTVEEFOMZ
NPWFPWFSPOFBOPUIFS4FJTNJDXBWFTUSBWFMPVUGSPNUIFGPDVTBMMBSPVOEUIF
&BSUI4IPXTUVEFOUTIPXXFDBOVTFUIFFFDUTPGTFJTNJDXBWFTUPOEPVUBCPVU
UIFTUSVDUVSFPGUIF&BSUI-PWFXBWFT-XBWFTUSBWFMBSPVOEUIF&BSUITTVSGBDF
BOEBSFSFTQPOTJCMFGPSNPTUPGUIFEBNBHFUPCVJMEJOHT1XBWFTQSJNBSZPS
QSFTTVSFUSBWFMGBTUFSUIBO4XBWFTTFDPOEBSZPSTIFBSBOEDBOUSBWFMUISPVHI
CPUITPMJEBOEMJRVJE4XBWFTDBOPOMZUSBWFMUISPVHITPMJET#ZFYBNJOJOHXIBU
XBWFTBSFEFUFDUFEBUWBSJPVTQMBDFTPOUIF&BSUITTVSGBDFBOEUIFMFOHUIPGUJNF
JUUBLFTGPSFBDIUZQFPGXBWFUPBSSJWFTDJFOUJTUTIBWFDBMDVMBUFEUIFTJ[FBOE
TUSVDUVSFPGUIF&BSUITDPSF
Grade 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
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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
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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
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#ZUIFFOEPGUIJTTFDUJPOTUVEFOUTTIPVMECFBCMFUP
t 4UBUFUIFXBWFFRVBUJPOBOEVTFJUUPTPMWFQSPCMFNT
t %FTDSJCFUIFDIBSBDUFSJTUJDQSPQFSUJFTPGXBWFTJODMVEJOHSFGMFDUJPO
SFGSBDUJPOEJGGSBDUJPOBOEJOUFSGFSFODF
t %FGJOFUIFUFSNTEJGGSBDUJPOBOEJOUFSGFSFODF
Starting off
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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
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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
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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
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Reflection and refraction
SA
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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
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#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
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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
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FTF GSFRVFODJFT
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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
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MA
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CA
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Uses of sound waves
SA
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JOGPSNBUJPO
MA
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CA
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Activities
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hear ultrasound?
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Resources
IUUQXXXNFEJBDPMMFHFDPNBVEJPTPVOEXBWFTIUNM
Grade 9
109
6OJU8BWFNPUJPOBOETPVOE
Answers to review questions
B 4PVOEUSBWFMTGBTUFSUISPVHITPMJETUIBOMJRVJETGBTUFSUISPV
gases.
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-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
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GSFRVFODZ)[XBWFMFOHUIN
TQFFENTQFSJPET
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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
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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
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QSPCMFNTPMWJOHBQQMZJOHDPODFQUTNFBTVSJOHNBLJOHDPOD
JOUFSQSFUJOHJMMVTUSBUFEEBUB
Motion in a straight line
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t.FOUJPOUIFWBSJBUJPOPGBDDFMFSBUJPOEVFUPHSBWJUZPOUIFTVS
FBSUI
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t1MPUv–tHSBQIGSPNWFMPDJUZBOEUJNFEBUBQSPWJEFEJOBUBCMF
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Force and Newton’s laws t*EFOUJGZGPSDFTJOOBUVSF
of motion
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112
Grade 9
Grade 9: Physics Minimum Learning Competencies
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t%FOFJNQVMTFBOEEFTDSJCFUIFSFMBUJPOCFUXFFOJNQVMTFBOEM
NPNFOUVN
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t&YQMBJOUIFTUBUFPGXFJHIUMFTTOFTT
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POBCPEZ
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UPBDFMMJOH
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t&YQMBJOUIFEJFSFODFTCFUXFFOMJNJUJOHTUBUJDBOETMJEJOHG
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BOEOPSNBMGPSDF
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t4UBUF/FXUPOTJSEMBXBOEHJWFFYBNQMFTXIFSFJUJTBQQMJFE
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t%FNPOTUSBUFTDJFOUJDFORVJSZTLJMMTTVDIBTPCTFSWJOHDPNQ
DMBTTJGZJOHQSPCMFNTPMWJOHBQQMZJOHDPODFQUTNBLJOHDP
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Work, energy and power t%FOFUIFUFSNXPSL
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FOFSHZ
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t$BMDVMBUFUIFHSBWJUBUJPOBMQPUFOUJBMFOFSHZPGBCPEZJOH
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DPMMJTJPOT
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NFDIBOJDBMTZTUFN
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Grade 9
113
Grade 9: Physics Minimum Learning Competencies
t%FNPOTUSBUFTDJFOUJDFORVJSZTLJMMTTVDIBTPCTFSWJOHQSFEJD
DMBTTJGZJOHDPNNVOJDBUJOHQSPCMFNTPMWJOHBTLJOHRVFTUJP
DPODMVTJPOTJOUFSQSFUJOHJMMVTUSBUJPOTSFMBUJOHDBVTFBO
DPODFQUEFTJHOJOHFYQFSJNFOUT
Simple machines
t%FTDSJCFUIFQVSQPTFPGNBDIJOFT
t-JTUUIFTJNQMFNBDIJOFTBOEFYQMBJOUIFJSVTFT
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t$BMDVMBUFUIF."73BOEFDJFODZPGTJNQMFNBDIJOFT
t$BUFHPSJTFTJNQMFNBDIJOFTBTGPSDFNVMUJQMJFSPSTQFFENVMUJ
EJSFDUJPODIBOHFS
t&YQMBJOUIFSPMFPGTJNQMFNBDIJOFTJOUFDIOPMPHZ
t%FNPOTUSBUFTDJFOUJDFORVJSZTLJMMTTVDIBTPCTFSWJOHDMBTT
DPNNVOJDBUJOHDPNQBSJOHESBXJOHDPODMVTJPOTNFBTVSJOHBT
RVFTUJPOTEFTJHOJOHFYQFSJNFOUQSPCMFNTPMWJOHBQQMZJOH
JOUFSQSFUJOHJMMVTUSBUJPOTNBLJOHNPEFMT
Fluid statics
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t%FOFUIFUFSNTQSFTTVSFEFOTJUZSFMBUJWFEFOTJUZ
t*EFOUJGZVOJUTVTFEUPNFBTVSFQSFTTVSF
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t*EFOUJGZUIBUQSFTTVSFEVFUPBMJRVJEBUSFTUEFQFOETPOEFQUI
t%FNPOTUSBUFUIFSFMBUJPOTIJQCFUXFFOQSFTTVSFGPSDFBOEBSFB
t$BMDVMBUFUIFQSFTTVSFEVFUPBMJRVJEBUSFTUBUBOZEFQUI
t$POWFSUQSFTTVSFWBMVFTGSPNPOFVOJUUPBOPUIFS
t&YQMBJO1BTDBMTQSJODJQMFBOEJUTBQQMJDBUJPO
t&YQMBJO"SDIJNFEFTTQSJODJQMFBOEJUTBQQMJDBUJPO
t&YQMBJOPUBUJPOQSJODJQMF
t*EFOUJGZUIFGPSDFTBDUJOHPOBCPEZUIBUJTJNNFSTFEPSPBUJOHJO
t%FNPOTUSBUFUIFVOEFSTUBOEJOHPGCVPZBOUGPSDFBOEUIFSFMBU
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t%FOFUIFUFSNTTVSGBDFUFOTJPODPIFTJPOBEIFTJPO
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BUNPTQIFSJDQSFTTVSF
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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
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Wave motion and sound t%FOFUIFUFSNTXBWFQVMTFUSBJOPGXBWFT
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BNQMJUVEF
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DPODFQUT
Grade 9
115
Physics syllabus
General objectives of Grade 9 physics
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TPVOEMJHIUUIFSNBMBOEUIFXBZFOFSHZJTUSBOTGPSNFEBOEUSBOTN
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FOWJSPONFOU
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Unit 1: Vectors (9 periods)
Unit outcomes: Students will be able to:
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BEEJUJPOBOETVCUSBDUJPOBOEQSPQFSUJFTPGWFDUPST
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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)
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BOBMZUJDBMMZ
t "OBMZUJDBM
PGUIFVOTFFOJTJNQPSUBOU4UVEFOUTTIPVMEMJTUB
UIFDPODFQUTJOQIZTJDTUIBUBSFAVOTFFOCVUNVTU
t 3FQSFTFOUWFDUPSTt(SBQIJDBM
CFSFBM4UVEFOUTTIPVMECFBCMFUPBEEBOETVCUSB
HSBQIJDBMMZ
WFDUPSTHSBQIJDBMMZCZUIFUJQUPUBJMNFUIPEPSU
t "EEUXPWFDUPSTBMPOH
1.2 Addition and
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the same direction, in subtraction of vectors.
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opposite directions and (5 periods)
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at right angles to each
t(SBQIJDBMMZ
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PUIFS
t#ZDPNQPOFOUNFUIPET
5IFO&BTUN4UVEFOUTBDUPVUUIFEJSFDUJPOTJOUIF
t 4QFDJGZUIFEJSFDUJPO
QSPCMFN8IFOUIFQSPCMFNJTDPNQMFUFEUIFZNFBTV
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1.3 Some applications of UIFEJTUBODFGSPNUIFTUBSUJOHQPJOU5IFZDPQZUIF
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vectors (2 periods)
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t 'JOEUIFNBHOJUVEF t&YQFSJNFOUBMBQQSPBDI
NBUIFNBUJDBMMZBOEDPNQBSFBOTXFST
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SFTVMUBOUPGUXPPS
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NPSFWFDUPSTVTJOHUIF
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t 6TFR=(Rx2 + Ry2)
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to determine the
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NBHOJUVEFPGUIF
SFTVMUBOUWFDUPST
Sample: Peer instruction:
t "QQMZUBOæ=
Is this system in equilibrium?
y/RxRto
determine the direction
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t 'JOEUIFBOHMFPGUIF
SFTVMUBOUWFDUPSR makes
with respect to the
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ZFT
t 6TFUIFBQQSPQSJBUFTJHO
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2) no
components in the
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TPMVUJPOPGQSPCMFNT
5IFUJQUPUBJMCSJOHTBTVNPG[FSPTPZFT
t %FåOFUIFUFSN
5XPGPSDFWFDUPSTBDUJOHPOBOPCKFDUDBOBEEUP
FRVJMJCSJVN
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BEEUPBTVNPG[FSP
ZFT
2) no
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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
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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,
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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
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5IFLFZJEFBJTDSFBUJOHUIFBDDVSBUFWFMPDJUZWTUJNFH
*OQSFWJPVTVOJUT(SBEFTBOEXFKVTUQMPUUFEBWFSBHF
WFMPDJUZWFSTVTUJNF5IJTDIBQUFSUBLFTBEFFQFSMPPL
BWFSBHFWFMPDJUZSFBMMZJTUIFJOTUBOUBOFPVTWFMP
QPJOU
"DUJWJUZ
.PEFMUIJTXJUIBQFSTPOXBMLJOHCFUXFFOUXPQPJOUTFW
XJUIBWFSZVOFWFOWFMPDJUZJODMVEJOHCBDLXBSET5IF
POMZSVMFTBSFUIBUBGUFSTFDPOETUIFTUVEFOUNVTUCF
the endpoint and DN"TLTPNFPOFUPEPBRVBMJUBUJWF
HSBQIBUUIFTBNFUJNFBTUIFXBMLJOHPGWTU*UNJHIU
CFRVJUFKBHHFEBOEOPOMJOFBSFWFODSPTTJOHUIFBYJT
TIPXCBDLXBSETNPUJPO%PBOPUIFSKBHHFEXBMLVOEFSUI
same conditions tTBOEdN5IFBWFSBHFWFMPDJUZJT
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"UTPNFQPJOUJOUIFUJNFUIFQFSTPO.645IBWFHPOFBU
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DPOTUBOUMZDIBOHJOH8IBUQPJOUXFEPOULOPXCVUWFM
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KVNQGSPNPOFQMBDFUPBOPUIFS*OTUBOUBOFPVTWFMPD
CFJNNFBTVSBCMFCVUUIFSFBSFXBZTUPDBMDVMBUFJU
t *GUIFWFMPDJUZJTDPOTUBOUMZJODSFBTJOHPWFSBOJO
OPKBHHFENPUJPOTUIFOUIFBWFSBHFWFMPDJUZNVTUCF
JOTUBOUBOFPVTWFMPDJUZBUUIFUJNFNJEQPJOU5IJTJT
JEFB*UGVOEBNFOUBMMZJTUIFNFBOWBMVFUIFPSFNGPS
as Vinstant at t mid (mid
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BWH
point)
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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
4IJGUJUPWFSN"EENBOETUBSUUIFSF5IFQPJOUJTUIBU
UIFEBUBJTSFMBUJWFUPUIFJOTUSVNFOU8FBMSFBEZLOPX
BMMQPTJUJPOJTSFMBUJWFQPTJUJPOEFQFOETPOUIF[FSP
PGUIFSVMFS"MMUJNFJTSFMBUJWFBHBJOXIBUJTUIFTUBSU
QPJOUJOUJNF 4UVEFOUTTIPVMEBQQSFDJBUFUIBUBMMWF
JTSFMBUJWF*UEFQFOETPOUIFGSBNFGSPNXIJDIZPVBSF
PCTFSWJOH4UVEFOUTXJMMHJWFFYBNQMFTPGGSBNFTJO
TPNFPCKFDUTBQQFBSUPCFNPWJOHCVUBSFTUBUJPOBSZ
PXOGSBNF5IFTUVEFOUTTIPVMEBQQSFDJBUFUIBUBMMQIZ
FRVBUJPOTBSFWBMJEJOFJUIFSDPOTUBOUWFMPDJUZNPW
OPONPWJOHGSBNFT5IFDPODFQUPGNPWJOHPSOPONPWJ
EFQFOEFOUPOUIFPCTFSWFS
Assessment
FUFBDIFSTIPVMEBTTFTTFBDITUVEFOUTXPSLDPOUJOVPVTMZPWFSUIFXIPMFVOJU
BOEDPNQBSFJUXJUIUIFGPMMPXJOHEFTDSJQUJPOCBTFEPOUIFDPNQFUFODJFTUP
EFUFSNJOFXIFUIFSUIFTUVEFOUIBTBDIJFWFEUIFNJOJNVNSFRVJSFEMFWFM
Students at minimum requirement level
"TUVEFOUXPSLJOHBUUIFNJOJNVNSFRVJSFNFOUMFWFMXJMMCFBCMFUPEFOFBOE
EFTDSJCFDPODFQUTBOEVOJUTSFMBUFEUPNPUJPOFHWFDUPSTTDBMBSTEJTQMBDFNFOU
VOJGPSNNPUJPOJOTUBOUBOFPVTBOEBWFSBHFWFMPDJUZVOJGPSNBDDFMFSBUJPO
JOTUBOUBOFPVTBOEBWFSBHFBDDFMFSBUJPOEFTDSJCFBOEFYQMBJOEJFSFOULJOETPG
NPUJPOBOEBQQMZRVBOUJUBUJWFMZSFMBUJPOTIJQTCFUXFFOEJTQMBDFNFOUWFMPDJUZ
BDDFMFSBUJPOJOSFMFWBOUQSPCMFNTJOUFSQSFUQBUUFSOTBOEUSFOETJOEBUBCZNFBO
PGHSBQITESBXOBOEJOGFSPSDBMDVMBUFMJOFBSBOEOPOMJOFBSSFMBUJPOTIJQTBNPOH
WBSJBCMFTFHBOBMZTFBOEFYQMBJOUIFNPUJPOPGPCKFDUTVTJOHEJTQMBDFNFOUoUJNF
HSBQITWFMPDJUZoUJNFHSBQITBOEBDDFMFSBUJPOoUJNFHSBQIT
Students above minimum requirement level
4UVEFOUTXPSLJOHBCPWFUIFNJOJNVNSFRVJSFNFOUMFWFMTIPVMECFQSBJTFEBOE
UIFJSBDIJFWFNFOUTSFDPHOJTFEFZTIPVMECFFODPVSBHFEUPDPOUJOVFXPSLJOH
IBSEBOEOPUCFDPNFDPNQMBDFOU
Students below minimum requirement level
4UVEFOUTXPSLJOHCFMPXUIFNJOJNVNSFRVJSFNFOUMFWFMXJMMSFRVJSFFYUSBIFMQJG
UIFZBSFUPDBUDIVQXJUISFTUPGUIFDMBTTFZTIPVMECFHJWFOFYUSBBUUFOUJPOJO
DMBTTBOEBEEJUJPOBMMFTTPOUJNFEVSJOHCSFBLTPSBUUIFFOEPGUIFEBZ
Grade 9
123
Grade 9: Physics syllabus
Unit 3: Forces and Newton’s Laws of motion (19 periods)
Unit outcomes: Students will be able to:
t(BJOLOPXMFEHFBOEVOEFSTUBOEJOHTPOGPSDFTJOHFOFSBMMBXTPG
MJOFBSNPNFOUVNBOEJNQVMTFDPOTFSWBUJPOPGMJOFBSNPNFOUVN
STUDPOEJUJPOPGFRVJMJCSJVN
t%FWFMPQTLJMMTJOSFTPMWJOHBOEDPNQPTJOHGPSDFTBQQMZJOH/F
PGNPUJPOJOTPMWJOHQSPCMFNTVTJOHUIFMBXPGDPOTFSWBUJPOPG
NPNFOUVNESBXJOHGSFFCPEZEJBHSBNT
t"QQSFDJBUFUIFWFDUPSOBUVSFPGGPSDFUIFBQQMJDBUJPOPG/FXUPOT
MJGFBDUJWJUJFT
Competencies
Contents
Suggested activities
Students will be able 3. Forces and
5IFUFBDIFSJOWJUFTTUVEFOUTUPMJTUBMMUIFGPSDFTUIFZL
to:
Newton’s laws of
)FTIFHSPVQTUIFGPSDFTCZLJOEBTUIFTUVEFOUTPGGFS
motion
t -JTUUIFGPSDFTUIBU
TVHHFTUJPOT/POQIZTJDBMGPSDFTBSFQMBDFEUPPOFTJEF
PDDVSJOOBUVSF 3.1 Forces in nature JTJNQPSUBOUUPSFDPHOJTFUIFTFJEFBTQVCMJDMZ5IFTFBS
(2 periods)
UIFNJTDPODFQUJPOTUIBUBSFPGUFOWFSZIBSEUPPWFSDPN
t 4UBUF/FXUPOTåSTU
MBX
t 8IBUBSFQIZTJDBM FYBNQMFiUIFGPSDFUIBULFFQTBOPCKFDUNPWJOHwUIBUEP
OPUFYJTUCZ/FXUPOTåSTUMBX
t $BUFHPSJTFGPSDFTGPSDFT
as contact or nont $POUBDUBOEOPO 4BNQMFQIZTJDBMGPSDFT
DPOUBDU
DPOUBDUGPSDFT tHSBWJUZ
t &YQMBJOUIF
t/FXUPOTåSTUMBX t GSJDUJPOOPUFUIFUXPLJOETBOEUIBUGSJDUJPOJTBSBUIF
relationship between
TUSBOHFGPSDFJUPOMZBDUTBHBJOTUZPV:PVDBOEPXPSL
NBTTBOEJOFSUJB
BHBJOTUGSJDUJPO
3.2 Newton’s second
t %JTUJOHVJTICFUXFFO
tFMFDUSJDBOENBHOFUJDGPSDF
law (2 periods)
elastic and inelastic
tCVPZBOUGPSDF
t8FJHIU
NBUFSJBMT
t8FJHIUMFTTOFTT "DUJWJUZ#SJEHJOHNFUBQIPSUPUIFåSTUMBX
t 4UBUF)PPLFTMBX
)BWFBA7USBDLoNMPOHXJUIBTIPSUFSiMBVODIwUSBDL5IF
t 3FBEUIFNBHOJUVEF
A7NVTUCFWFSZTNPPUINFUBMFJUIFSJSPOPSBMVNJOJVNMB
PGGPSDFVTJOHB 3.3 Frictional force
IPSJ[POUBMMZPOBUBCMFPSBSPXPGEFTLT6TFBMBSHFCFBS
QFSJPET
spring balance
)BWFBTUPQUPIBMUNPUJPO3PMMUIFCBMMEPXOB° ramp
t,JOETPGGSJDUJPO XJUIUIFTUPQBCPVUNGSPNUIFTUBSU.PWFUIFTUPQUP
t &YQSFTTUIF
t $BMDVMBUJOHGSJDUJPO
dimensions and
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BOEOPSNBMGPSDF
4*VOJUPGBGPSDF
CFMPXGSJDUJPO.PWFUIFTUPQUPNUIFOUPNUIFO
DPOTUBOUPGBTQSJOH
UPUIFFOE1FSIBQTBTMJHIUUJMUVOTFFONJHIUIFMQ8IBU
BCPVUUIFTQFFEPGUIFCBMM *UJTSFMBUJWFMZDPOTUBOU*
t %FUFSNJOFUIFTQSJOH
3.4 Newton’s third
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constant KPGB
law QFSJPET
JOWJUBUJPOUPTUBUF/FXUPOTåSTUMBX
TQSJOH
t-JOFBSNPNFOUVN
Peer Instruction:
t %FUFSNJOFUIF
t *NQVMTFBOE
BDDFMFSBUJPOPGB momentum
'SPNBEJBHSBNTBZBCPPLPOBUBCMFTUVEFOUTDPVOUUIF
body attached to the
OVNCFSPGGPSDFTPOJU
TQSJOHJOBWFSUJDBM
"OPUIFSEJBHSBN"QFSTPOQVTIJOHBQBDLBHFPOBýPPSXJUI
3.5 Conservation of
QPTJUJPO
GSJDUJPO
linear momentum
=
ma
to
t "QQMZF
net
$PVOUUIFGPSDFT
QFSJPET
TPMWFTPNFQSPCMFNT
"QFSTPOQVTIJOHBCMPDLVQBSBNQ$PVOUUIFGPSDFT
3.6 Collisions
"IFMJDPQUFSIPWFSJOHPWFSUIFHSPVOE$PVOUUIFGPSDFT
(2 periods)
/PUFDMBSJGZUIFFGGFDUTPGGPSDFTJOSFBMMJGFFYBNQM
t&MBTUJD$PMMJTJPOT
demonstration/experiments are required to be done by either
t*OFMBTUJD$PMMJTJPOT
ZPVPSUIFTUVEFOUT
124
Grade 9
Grade 9: Physics syllabus
Competencies
Contents
Students will be able 3.7 The rst condition
to:
of equilibrium
QFSJPET
t %JTUJOHVJTICFUXFFO
SFTVMUBOUGPSDFBOE
FRVJMJCSBOUGPSDF
t %FTDSJCFUIFFGGFDU
PGGPSDFBDUJOHPOB
CPEZ
t 3FTPMWFGPSDFT
acting on a body
into rectangular
DPNQPOFOUT
t $PNQPTFGPSDFT
acting on a body
using component
NFUIPET
t %FTDSJCFUIFXFJHIU
PGBCPEZ
t &YQMBJOXIZUIF
XFJHIUPGBCPEZ
WBSJFTPOUIFTVSGBDF
PGUIF&BSUI
t %JTUJOHVJTICFUXFFO
weight and apparent
XFJHIU
t &YQMBJOUIF
QIFOPNFOPOPG
XFJHIUMFTTOFTT
t $BMDVMBUFUIFUSVF
and apparent weight
PGBCPEZTVTQFOEFE
JOBNPWJOHFMFWBUPS
t &YQMBJOIPXGSJDUJPOBM
GPSDFEFQFOETPOUIF
OBUVSFPGTVSGBDFT
and the normal
DPOUBDUGPSDF
t %FTDSJCFUIF
EJGGFSFODFTCFUXFFO
the terms limiting
GSJDUJPOTUBUJD
GSJDUJPOLJOFUJD
GSJDUJPO
t %SBXBGSFFCPEZ
diagram representing
BMMUIFGPSDF
components acting
POBCPEZNPWJOH
along an inclined
QMBOF
Grade 9
Suggested activities
t %PGSFFCPEZEJBHSBNTGPSBHSFBUNBOZDPNNPOFYBNQ
*ODMVEFTPNFBDDFMFSBUJOHNPUJPOT
t%PTBNQMFDBMDVMBUJPOTBOEBTLTUVEFOUTUPEPTP
t %FNPOTUSBUFFYQFSJNFOUUPSFMBUFF, a, m using practic
FYBNQMFT&ODPVSBHFTUVEFOUTUPEJTDVTTUIFDPODFQ
XFJHIUBOEIPXJUJTEJGGFSFOUGSPNNBTT
Peer instruction:
%JBHSBN0CKFDULNPWFSUIF&BSUI
*TJUXFJHIUMFTT $BSET:FT/P
*UIBTMFTTXFJHIUUIBOPOUIF&BSUITTVSGBDF
%JBHSBN0CKFDUFYBDUMZCFUXFFO&BSUIBOE.PPO
*TJUXFJHIUMFTT $BSET:FT/P
/P5IF&BSUIQVMMTNPSFUIBOUIF.PPO7FSZMPXXFJHIU
%JBHSBN0CKFDUFYBDUMZCFUXFFOBCPVUžPGUIFXBZUPU
.PPO£PGUIFXBZUPUIF&BSUI
*TJUXFJHIUMFTT $BSET:FT/P
:FT5IF&BSUIQVMMTBCPVUUIFTBNFIFSFBTUIF&BSUIJTBCPV
UJNFTUIFNBTTPGUIF.PPO'NHTUJMMXPSLTIFSFCVU
the gJTDIBOHJOH"UUIBUTQFDJBMQPJOUUIFåSTU-BHSBOHJ
'PSDFGSPN&BSUIGPSDFGSPN.PPOBOEH-BUFSFYQMBJO
IPXJUWBSJFTXJUIUIFQPTJUJPOPOUIFFBSUITTVSGBDF6TJO
the equation w = mgBTLTUVEFOUTUPEPDBMDVMBUJPOT
-JTUUIFDBVTFTPGGSJDUJPO
*OWJUFJEFBT
3FBMMZHFPNFUSJDoWFSZSPVHITVSGBDFTMJLFTBOEQB
HSJOEJOHPOPOFBOPUIFS
0OTNPPUITVSGBDFTBUPNTPSNPMFDVMFTDBOBUUSBDU
DBVTFGSJDUJPOBMGPSDF
8IBUBSFUIFUXPLJOETPGGSJDUJPO
Peer instruction:
8IZJTTUBUJDGSJDUJPOHSFBUFSUIBOLJOFUJDGSJDUJPO
#FDBVTFUIFZNBLFNPSFSPVHIFEHFTXJUIQSFTTVSF
#FDBVTFUIFBUPNTPSNPMFDVMFTQSFTTUJHIUBOENBZIB
TPNFCPOEJOH
Peer instruction:
8IZEPFTBEEJOHPJMPSHSFBTFUPBTVSGBDFNBLFTMJEJOH
easier?
#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
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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?
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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?
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HPBMJFTUBZJOUIFBJS )PXGBSEPFTJUHP
$BMDVMBUFBNBYTQFFEPGBLJDL
%PBOPUIFSDBMDVMBUJPO,OPXJOHUIFTQFFEPGBWFSZGB
TPDDFSCBMMXIBUTQFFENVTUB,HTPDDFSQMBZFSIBWFUP
BUUBJOUIFTBNFNPNFOUVN*TUIJTGBTUPSTMPX
8IBUDBOZPVTBZBCPVUUIFTQFFEPGBLHTPDDFSQMBZFS
8IBUTQFFEXPVMEIFIBWFUPHPUPIBWFUIBUNPNFOUVN
4PMWFTJNQMFFYBNQMFTPONPNFOUVN
t (JWFBOFYFSDJTFPONPNFOUVNGPSUIFTUVEFOUTJOUIFD
&RVBMNPNFOUVNVOFRVBMNPNFOUVN
t/PDPOTFSWBUJPOZFU
127
Grade 9: Physics syllabus
Competencies
Contents
Suggested activities
4PMWFTJNQMFFYBNQMFTPOJNQVMTFBOENPNFOUVN
t (JWFBOFYFSDJTFPOJNQVMTFBOENPNFOUVNGPSUIFTUVEF
JOUIFDMBTT*NQVMTFIBTBWFSZTQFDJåDNFBOJOHJOQIZTJ
It does not mean anything like a mental idea or a will or a
XJTI
t 'PSDFJTXIBUDIBOHFTBOPCKFDUTWFMPDJUZ/FXUPOT
to v2 which
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IBQQFOFEGSPNUIFBDUJPOPGUIFGPSDFf
mv2omv p
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PWFSUJNF$POTJEFSUIFVOJUT
'PSDFYUJNF/UNTFDUJNF/UNTFD
5IJTIBTUIFTBNFVOJUTBTNPNFOUVN
3FMBUJPOCFUXFFONPNFOUVNBOEJNQVMTF
mV2omV P = Force × time
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&YBNQMFTPOJNQVMTFBOENPNFOUVN
t (JWFBOFYFSDJTFPOJNQVMTFBOENPNFOUVNGPSUIFTUVEF
JOUIFDMBTT
8JUIUIFEFåOJUJPOPGNPNFOUVNDPNJOHGSPN/FXUPOT
6OJWFSTBMMBXTUIFSFJTBOFXDPOTFSWBUJPOMBXoUIF
DPOTFSWBUJPOPGNPNFOUVN*UJTVOJWFSTBMBQQMZJOHG
BUPNTUPHBMBYJFT0OFDBOOPUMPTFPSHBJONPNFOUVNVO
BOZDPOEJUJPO
pinitial = pnal
r
r
Pinitial = Pnal
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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
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DPVQMFENBTTFTOPXNPWFXJUI
128
Grade 9
Grade 9: Physics syllabus
Competencies
Contents
Suggested activities
-FUUIFTUVEFOUTEPTJNQMFPOFEJNFOTJPOBMDPOTFSWBU
momentum problems (totally inelastic collisions) and impulse
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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:
2YNLN/
F LHLNT
5IFSFTVMUJTTVSQSJTJOHCVUJUGPMMPXTGSPNUIFGVOEB
MBXTPGQIZTJDT
"QQMJDBUJPOTJODMVEFEFTJHOJOHCVMMFUQSPPGWFTU
PGCVMMFUT*UJTTVSQSJTJOHIPXQPXFSGVMUIFTFGPSDFT
%PTPNFBEEJUJPOBMJNQVMTFFRVBUJPOTJOPOFEJNFOTJPO
OPGSJDUJPOXJUIUPUBMMZJOFMBTUJDDPMMJTJPOT&MBTUJ
NPSFDPNQMJDBUFEUPDBMDVMBUF8FXJMMEPTPNFFYBNQM
TJNQMFFMBTUJDDPMMJTJPOT*OBOFMBTUJDDPMMJTJPOLJO
DPOTFSWFE8FXJMMDBMDVMBUFPOMZVTJOHWFDUPSNPNFO
4BNQMFPOUIFCPBSE*OBTFSWFHUFOOJTSBDLFUTUSJLFTB
CBMMHPJOHLNT5IFUFOOJTCBMMIBTBNBTTPGH"GUFS
UIFDPMMJTJPOUIFTQFFEPGUIFSBDLFUJTLNT)PXGBTUEJE
UIFCBMMMFBWFUIFSBDLFU
4QFDJBMGBTUDBNFSBTIPXTUIBUUIFUJNFPGJOUFSBDUJPO
UIFCBMMBOEUIFSBDLFUJTT8IBUXBTUIFBWFSBHFGPSDF
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
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t %FTDSJCFUIF
4.1 Mechanical work XJUIPVUDPNNFOU5IFODBUFHPSJTFUIFNBTQIZTJDBMBOEO
necessary conditions (2 periods)
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GPSXPSLUPCFEPOF
t 8PSLEPOFCZB
%FåOJUJPO8PSLJOHFOFSBMGPSDFEJTQMBDFNFOUDPTæ
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t %FTDSJCFUIFXPSL t 8PSLEPOFCZB
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acting on a body at
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an angleæ to the
4.2 Work–energy
$MBTTEFNPOTUSBUJPOTXJUITUVEFOUJOWPMWFNFOUPGE
IPSJ[POUBM
theorem (2 periods)
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t 6TFW = FS cos æ
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UPTPMWFSFMBUFEt,JOFUJDFOFSHZ
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t1PUFOUJBMFOFSHZ
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t.FDIBOJDBMFOFSHZ mass hanging (manipulated by the student), a large, slow
t $BMDVMBUFUIFXPSL
EPOFCZBGPSDFPG
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HSBWJUZPOBCPEZ4.3 Conservation of
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t %JTUJOHVJTICFUXFFO
UIFCBDLi*ODSFBTJOH1&w0OFCZPOFJOUIFEFNPOTUSBUJPO
energy (6 periods)
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UIFTUVEFOUTTIPVMEXJUIWPJDFBOEDBSETDPNNFOUPOUIF
t 5IFMBXPG
XPSL
DPOTFSWBUJPOPGQSPDFTT4UBSUXJUIUIFQFOEVMVN4UVEFOUTFYQMBJOUIF
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t $BMDVMBUFUIFXPSLenergy
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EPOFCZBGSJDUJPOBM
t $PMMJTJPO4JOPOF
BTLTi8IFSFJTBGPSDFNPWJOHBDSPTTBEJTUBODF w
GPSDF
dimension
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t %FUFSNJOFUIFXPSL
t &OFSHZJOBO
EPOFCZBWBSJBCMF oscillating pendulum instructor increases the complexity by adding a card: “work
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GPSDF
t &OFSHZJOBTQSJOHo
"OEi8PSLEPOFCZUIFQFSTPOwBMTPi8PSLEPOFCZUIFSVCCF
t &YQMBJOUIF
mass system
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relationship between
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4.4 Mechanical power CFDPNFTQPUFOUJBMBOEUIFOCFDPNFTLJOFUJD
t %FSJWFUIF
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relationship between
Peer instruction on kinetic and potential energy:
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work and kinetic
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Grade 9
131
Grade 9: Physics syllabus
Competencies
Contents
Students will be able
to:
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problems using the
relationship between
work and kinetic
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between work and
potential energy as
W = –U.
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problems using
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mechanical energy
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elastic and inelastic
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collision in one
dimension using the
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132
Suggested activities
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Grade 9
Grade 9: Physics syllabus
Competencies
Contents
Students will be able
to:
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changes that
take place in an
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changes that
takes place in an
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wind energy, solar
energy, geothermal
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Suggested activities
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Peer instruction:
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Classroom demonstration: Suspend a rubber band between
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PEspring = k x 2 = mVv2 = KEmass
2
2
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Peer instruction:
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8IBUXPVMEIBQQFOJGUIFOVNCFSPGFMBTUJDTXFSFEPVCM
Grade 9
133
Grade 9: Physics syllabus
Competencies
Contents
Suggested activities
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must bang the ball as many times as possible per minute into
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Peer instruction:
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134
Grade 9
Grade 9: Physics syllabus
Competencies
Contents
Suggested activities
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cars will compete in a competition to see which one goes
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normal displacement component counts as distance Students
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car and explain their design decisions
Grade 9
135
Grade 9: Physics syllabus
Assessment
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Students at minimum requirement level
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Students above minimum requirement level
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Students below minimum requirement level
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136
Grade 9
Grade 9: Physics syllabus
Unit 5: Simple machines (11 periods)
Unit outcomes: Students will be able to:
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Competencies
Contents
Suggested activities
Students will be able 5. Simple machines
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to:
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5.1 Purposes of
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output, work
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t
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pulley
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or destroyed, the work output cannot exceed the input energy
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inclined plane with
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Grade 9
137
Grade 9: Physics syllabus
Competencies
Contents
Students will be able
to:
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(when the load is
on the axle on the
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machines are
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speed multiplier or
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138
Suggested activities
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the kitchen and note how many are machines?
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simple machine) including automobiles, bicycles, clocks and
photocopy machines
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machines, including automobiles and household appliances
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may include electrical and thermal elements, their mechanical
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JODMJOFEQMBOF
Grade 9
Grade 9: Physics syllabus
Competencies
Contents
Suggested activities
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FMCPXZPVSGPSFBSNTBSFBDUJOHBTBUIJSEDMBTTMFWFS
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SFTQPOE
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Card 2 bottle opener?
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Assessment
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BOEDPNQBSFJUXJUIUIFGPMMPXJOHEFTDSJQUJPOCBTFEPOUIFDPNQFUFODJFTUP
EFUFSNJOFXIFUIFSUIFTUVEFOUIBTBDIJFWFEUIFNJOJNVNSFRVJSFEMFWFM
Students at minimum requirement level
"TUVEFOUXPSLJOHBUUIFNJOJNVNSFRVJSFNFOUMFWFMXJMMCFBCMFUPJEFOUJGZ
EFTDSJCFBOEJMMVTUSBUFBQQMJDBUJPOTPGUZQFTPGTJNQMFNBDIJOFTUIBUJTUIF
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Students above minimum requirement level
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UIFJSBDIJFWFNFOUTSFDPHOJTFEFZTIPVMECFFODPVSBHFEUPDPOUJOVFXPSLJOH
IBSEBOEOPUCFDPNFDPNQMBDFOU
Students below minimum requirement level
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UIFZBSFUPDBUDIVQXJUISFTUPGUIFDMBTTFZTIPVMECFHJWFOFYUSBBUUFOUJPOJO
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Grade 9
139
Grade 9: Physics syllabus
Unit 6: Fluid statics (12 periods)
Unit outcomes: Students will be able to:
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VJEQSFTTVSFBUSFTUBUNPTQIFSJDQSFTTVSFBOENFBTVSFNFOUPGQS
t(BJOLOPXMFEHFBOEVOEFSTUBOEJOHPO1BTDBMTQSJODJQMF"SDIJNFE
TQSJODJQMFBOEPUBUJPOBOEUIFJSBQQMJDBUJPOT
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BOENFBTVSFNFOUPGQSFTTVSFVTJOHNFBTVSJOHEFWJDFT
t%FWFMPQJOUFSFTUBOEDVSJPTJUZJOQSPQFSUJFTPGVJET
t"QQSFDJBUFUIFSPMFPGBUNPTQIFSJDQSFTTVSFJOUFDIOPMPHZ
Competencies
Contents
Suggested activities
Students will be able 6. PFluid statics
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to:
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6.1 Air pressure
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t %FåOFUIFUFSN
(5 periods)
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t 5IFNBHOJUVEFPGBJS
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t 6TFUIFEFåOJUJPO pressure
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t "JSQSFTTVSFBOE
"DUJWJUZ
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t %FTDSJCFBUNPTQIFSJD
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6.2 Fluid pressure
atmospheric pressure, you must relate it to something with
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pressure with
as p= F/A, you can calculate the pressure you exert on the
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depth
measure atmospheric
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principle
is equal to one
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1B
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5
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between liquids and
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pressure exerted by air can be demonstrated in a dramatic
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pressure in a liquid
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UIFQMVOHFSTBQBSU$BOZPVEPJU
140
Grade 9
Grade 9: Physics syllabus
Competencies
Contents
Students will be able
to:
t "QQMZUIFGPSNVMB
p = ghUPTPMWF
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pressure on a body
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total =
Patm + gh
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principle to explain
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t "QQMZ1BTDBMT
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t &YQMBJOUIFVTFPG
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t %FNPOTUSBUF
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atmospheric pressure,
gauge pressure and
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absolute pressure and
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t $BMDVMBUFUIF
absolute and gauge
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BDPOUBJOFS
t 4UBUF"SDIJNFEFTT
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t %JTUJOHVJTICFUXFFO
true weight and
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CPEZ
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Grade 9
Suggested activities
$PODFQUTUPJOWFTUJHBUFNFBTVSJOHBUNPTQIFSJDQSF
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"TJNQMFBOFSPJECBSPNFUFSDBOCFNBEFGSPNIPVTFIPME
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BXJEFNPVUIFEFNQUZKBSBOETFBMJUXJUIBTIFFUPG.ZMBS
.ZMBSJTVTFEJOBMVNJOJTFEQBSUZCBMMPPOTJTSFMBUJW
impermeable to gas, and thereby allows balloons to remain
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OPPEMFCSPPNTUSBXUPUIFHVN5IFOFFEMFDBOQJWPUPO
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EPXO$POWFSTFMZJGUIFBUNPTQIFSJDQSFTTVSFJODSFBT
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calibrate your barometer, tune your radio to a local station
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UXPXFFLQFSJPEEFUFSNJOFJGUIFSFJTBSFMBUJPOTIJQCF
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Text:
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= p(rhc)gh, since gJTDPOTUBOUBOEUIFEFOTJUJFTPGNPTU
ýVJETBSFSFMBUJWFMZDPOTUBOUXJUIEFQUIUIFQSJODJQB
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5IFQSFTTVSFBUBOZMFWFMCFOFBUIUIFTVSGBDFPGBýVJE
JTUIFTBNFJOBMMEJSFDUJPOT*GGPSFYBNQMFBCBMMPPO
submerged in water, it will assume a smaller spherical shape
as water presses equally upon it in all directions, rather than
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submerged balloon transmits pressure equally in all directions
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1BTDBMTQSJODJQMFTUBUFTUIBUýVJETUSBOTNJUQSFTTV
JOBMMEJSFDUJPOT
141
Grade 9: Physics syllabus
Competencies
Contents
Students will be able
to:
t 4UBUFUIFQSJODJQMFPG
ýPUBUJPO
t &YQMBJOXIZCPEJFT
ýPBUPSTJOL
t $BMDVMBUFUIFEFOTJUZ
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PSEFOTJUZPGBýVJE
VTJOHýPUBUJPO
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142
Suggested activities
"DUJWJUZ$POTUSVDUB6UVCFCZCFOEJOHBTFDUJPOPGHMB
UVCJOH"MUFSOBUJWFMZZPVNBZVTFUXPTUSBJHIUQJFDFTP
HMBTTDPOOFDUFECZBOBSDPGýFYJCMFUVCJOH"EEXBUFSU
UIF6UVCFVOUJMJUJTBQQSPYJNBUFMZIBMGGVMM.FBTVSFU
IFJHIUPGUIFXBUFSJOCPUIBSNTBOESFDPSEJUJOBUBCMF
6TJOHBQBJSPGTDJTTPSTDVUBTFDUJPOGSPNBMBSHFCBMM
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FOEPGUIF6UVCF*NNFSTFUIFGVOOFMJOXBUFSBOESFDPSE
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UIFDPMVNOPGXBUFSJOUIFPQFOTJEFPGUIF6UVCFJOEJDBUF
BOJODSFBTFJOQSFTTVSFPOUIFGVOOFMNFNCSBOF$BSFGV
measure the change in height within the tube and record it
JOUIFUBCMF*OWFSUUIFGVOOFMLFFQJOHUIFNFNCSBOFBUU
TBNFMFWFMCVUGBDJOHUIFSFWFSTFEJSFDUJPO"HBJOSFDP
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UIFGVOOFMIPSJ[POUBMMZTPUIBUUIFNJEEMFPGUIFGVOOFM
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NFBTVSFNFOUT8IBUJTUIFJOýVFODFPGEFQUIPOQSFTTVSF
0OUIFCBTJTPGZPVSEBUBJTýVJEQSFTTVSFEJSFDUJPOBM *T
pressure greater in one direction than another?
"SDIJNFEFTTUBUFEUIBUBOZPCKFDUTVCNFSHFEPSýPBUJOH
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XJMMTJOLCFDBVTFJUTXFJHIUFYDFFETUIFCVPZBOUGPSDF*
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GPSDF
"DUJWJUZ
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6TJOH"SDIJNFEFTTQSJODJQMFMFUUIFTUVEFOUTFYQMBJOX
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"DUJWJUZ
'PSNBHSPVQBNPOHUIFTUVEFOUTUPDBMDVMBUFUIFCVPZBO
GPSDF
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SFDPSEJUTXFJHIUJOUIFUBCMF'JMMBCFBLFSXJUIXBUFSVOU
JUPWFSýPXT0ODFXBUFSIBTTUPQQFEýPXJOHQMBDFBESZ
HSBEVBUJOHDZMJOEFSPSPUIFSDPOUBJOFSCFOFBUIUIFTQP
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JUJOUIFCFBLFSTVDIUIBUBMMPGUIFEJTQMBDFEXBUFSýPXT
PWFSUIFTQPVUBOEJOUPUIFHSBEVBUJOHDZMJOEFS3FDPSE
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displaced can be measured by collecting and weighing all
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measured in air or in water?
Grade 9
Grade 9: Physics syllabus
Assessment
FUFBDIFSTIPVMEBTTFTTFBDITUVEFOUTXPSLDPOUJOVPVTMZPWFSUIFXIPMFVOJU
BOEDPNQBSFJUXJUIUIFGPMMPXJOHEFTDSJQUJPOCBTFEPOUIFDPNQFUFODJFTUP
EFUFSNJOFXIFUIFSUIFTUVEFOUIBTBDIJFWFEUIFNJOJNVNSFRVJSFEMFWFM
Students at minimum requirement level
"TUVEFOUXPSLJOHBUUIFNJOJNVNSFRVJSFNFOUMFWFMXJMMCFBCMFUP EFOF
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JOMJRVJETBOEHBTFTTUBUF1BTDBMTQSJODJQMFBOEFYQMBJOJUTBQQMJDBUJPOTJOUIF
USBOTNJTTJPOPGGPSDFTJOVJETZTUFNTTUBUF"SDIJNFEFTTQSJODJQMFBOEFYQMBJO
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Students above minimum requirement level
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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:
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FYQBOTJPOPGTVCTUBODFTRVBOUJUZPGIFBUBOEDIBOHFPGTUBUF
t%FWFMPQTLJMMTJODPNQVUJOHUIFBNPVOUPGIFBUTQFDJDDBQBDJUZ
IFBUBOEUIFSNBMFYQBOTJPOPGNBUFSJBMT
t"QQSFDJBUFUIFJNQPSUBODFPGUIFIJHIWBMVFPGTQFDJDIFBUDBQBDJU
BCOPSNBMFYQBOTJPOPGXBUFS
Competencies
Contents
Suggested activities
Students will be able 7. Temperature and
%FNP
to:
heat
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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
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t)FBUBOEUFNQFSBUVSF
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t %FåOFUIFUFSN
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bands to the wire, and then attach that to a board shaped
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t )FBUBTNPMFDVMBSMJLFBUFOOJTSBDLFU5IFCBMMTIPVMECPVODFPGGJUFBTJM
t %FTDSJCFUIFUIFSNBM
motion
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t 'JSTUMBXPG
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t %FSJWFUIFFYQSFTTJPO
thermodynamics
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GPSMJOFBSFYQBOTJPO
t 4FDPOEMBXPG
*HOPSFUIFTUVEFOUXIJMFZPVJOWJUFUIFDMBTTUPTIBSFJEF
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thermodynamics
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t %FSJWFUIFFYQSFTTJPO
RVBMJUBUJWF
*TJUBýVJE *TIFBUBUIJOH
GPSTVSGBDFBSFBM treatment)
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KPC$POUJOVFQPMMJOHUIFTUVEFOUTGPSJEFBTPGIFBU$PV
t 'JOEUIFSFMBUJPOTIJQ
7.2 Expansion of
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solids, liquids and
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gases QFSJPET
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"GUFSBCPVUNJOVUFTUBLFUIFUFNQFSBUVSFPGUIFCBMM
t .FOUJPOBQQMJDBUJPOT
8IZEJEJUHPVQ
7.3 Quantity of heat,
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*OWJUFBOTXFST$PVMEIFBUCFBýVJEGSPNUIJTFYQFSJNFOU
specic heat capacity
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and heat capacity
(bimetallic strip,
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thermostat)
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t 4PMWFQSPCMFNT t )FBUFYDIBOHF
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7.4 Changes of state
QFSJPET
t %JTUJOHVJTICFUXFFO
apparent and real
t-BUFOUIFBU
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t 4PMWFQSPCMFNT
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oT= V
t &YQMBJOUIFBCOPSNBM
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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 $BMDVMBUFUIFIFBU
DBQBDJUZPGBCPEZ
t &YQMBJOUIF
TJHOJåDBODFPGIJHI
TQFDJåDIFBUDBQBDJUZ
PGXBUFS
t 4PMWFQSPCMFNT
JOWPMWJOHIFBU
exchange using the
relationship heat lost
IFBUHBJOFE
t %FTDSJCFUIFVTFTPG
BDBMPSJNFUFS
t %FåOFUIFUFSN
latent heat
t %FåOFUIFUFSNT
MBUFOUIFBUPGGVTJPO
BOEMBUFOUIFBUPG
WBQPSJTBUJPO
t 4PMWFQSPCMFNT
JOWPMWJOHDIBOHFPG
TUBUF
Grade 9
Suggested activities
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iUBMLUPBUPNTw*UJTBSJEJDVMPVTTUJDLXJUIGFBUIFSTCF
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IPMETUIFTUJDLOFBSUIFCBMMBOEUIFQBEEMFPOUPQPGUIF
TUJDLi*XBOUBMMPGZPVBUPNTJOTJEFUPTUBSUNPWJOHJO
TBNFEJSFDUJPOVQBOEEPXOBOETUBSUCPVODJOHw/PUIJO
IBQQFOTIFNPWFTUPBOPUIFSUBCMFBOEBTLTTUVEFOUTUP
IFMQ
8IZDBOOPUBMMUIFBUPNTEFDJEFUPNPWFJOPOFEJSFDUJP
upwards and then start bouncing again?
*OWJUFTUVEFOUSFTQPOTFT
Students should appreciate that heat is totally random motion
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UPTPNFUIJOHMJLFLJOFUJDFOFSHZPGBCPEZ)FBUJTNPUJP
FOFSHZBUBOBUPNJDBOENPMFDVMBSMFWFM5IFSFJTOPXB
DPOWFSUUIBULJOEPGNPUJPOJOUPTPNFUIJOHFMTFMJLFL
FOFSHZ
5IJTJTUIFTFDPOEMBXPGUIFSNPEZOBNJDT*UMJLF/FXUPOT
MBXTBOEUIFDPOTFSWBUJPOMBXTJTPOFPGUIFHSFBUVOJ
QSJODJQMFT3BOEPNNPUJPODBOOPUCFVOEPOF*UBMTPN
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4UVEFOUTBMSFBEZLOPXUIFåSTUMBXJUJTUIFDPOTFSWBU
FOFSHZ
)BWFBTIFFUPGNFUBMXJUIBIPMFJOJUBOEBCBMMUIBUåUT
SJHIUJOXIFODPME*GUIFTIFFUJTIFBUFEXJMMUIFCBMMBMT
in?
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XJMMUIFCPMUåUJO 8IZ
%FNPOTUSBUJPO)BWFBCBMMPPOUFUIFSFEBUBJSUFNQFS
.FBTVSFJUTDJSDVNGFSFODF)PMEJUPWFSBDBOEMFýBNFB
TVGåDJFOUEJTUBODFOPUUPJOKVSFUIFSVCCFSGPSBGFX
UPIFBUUIFBJS.FBTVSFUIFEJBNFUFSPGUIFCBMMPPO
%JTDVTTUIFCBTJDLJOFUJDUIFPSZPGNBUUFSXJUITUVEFOU
RVBMJUBUJWFMZ
t 4UBUFUIFFGGFDUPGUFNQFSBUVSFPOUIFNPUJPOPGQBS
RVBMJUBUJWFMZ
t3FDBQJUVMBUFUIFFGGFDUTPGIFBUJOHBCPEZ
t %FNPOTUSBUFFYQBOTJPOPGTPMJETMJRVJETBOEHBTFT
1SFTFOUBUJPO4IPXUIFHSBQIPGUIFIFBUOFFEFEUPSBJTF
HSBNPGXBUFSGSPN¦°$UP°$
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PSBOBMDPIPMMBNQ6TFBTNBMMBNPVOU8IFOJUJTCPJMJO
LFFQSFBEJOHUIFUFNQFSBUVSF
8IZJTJUOPUJODSFBTJOH )FBUJTHPJOHJO
5FYUJOUSPEVDFTMBUFOUIFBUPGWBQPSJTBUJPOKH,TGPS
XBUFS
145
Grade 9: Physics syllabus
Competencies
Contents
Suggested activities
*OUSPEVDFMBUFOUIFBUPGNFMUJOHGVTJPOGPSXB
(SPVQXPSLoBTTFTTNFOUBTTJHOFBDIHSPVQPGo
TUVEFOUTBTQFDJåDBNPVOUPGXBUFSJOBKBSPSDV
.BLFJUSBOHFGSPNHUPLH)PXNVDIIFBUXJMM
JUUBLFUPHFUUIBUBNPVOUPGXBUFSUP°C?
Assessment
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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
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(string, spring, water,
UPQPGUIFXBWFNVTUNPWFBUFYBDUMZPOFEFTLFWFSZCF
TFJTNJD
PGUIFQFOEVMVNFWFSZPOFPSQSFGFSBCMZUXPTFDPOET
8.4 Sound waves
t *EFOUJGZUIBU
UFBDIFSTUBSUTUIFXBWFBUUIFGSPOUFOEOPUJOUIFNJEEM
QFSJPET
BTPVOEXBWFJT
5IJTSPXPGTUVEFOUTQSBDUJDFTNBLJOHUIFXBWFNPWFXJ
t 1SPEVDUJPOBOE
a longitudinal
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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
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NPWFGSPNUIFGSPOUUPUIFCBDLUIFOUPUIFGSPOUBHBJO
5IFSVMFJTUIBUUIFUPQPGUIFXBWFNVTUNPWFBUPOFEFTL
QFSQFOEVMVNIJU4UVEFOUTUJNFUIFXBWF5IFZNFBTVSFUIF
EJTUBODFCFUXFFOUIFNJEEMFPGUIFEFTLT5IFZDBMDVMBUF
TQFFEJONFUSFTQFSTFDPOE
-BCTJNVMBUJPO6TJOHBCSJEHJOHNFUBQIPSJEFBUIF
JOTUSVDUPSJOWJUFTUIFTUVEFOUTUPNBLFBNPEFMPGUIFX
QFBLUPQFBLJTPOFEFTL)FUBLFTBQJFDFPGIPTFUPWJTJCMZ
NPEFMUIFXBWFCFUXFFOUXPEFTLT.BLFUIFIPTFBCPVU
NMPOH*UNBLFTBTIBQFMJLFQBSUPGBTJOFXBWF5IJTJTPOF
DZDMFPGUIFXBWF5IJTJTBOFYDFQUJPOBMMZJNQPSUBOUJE
5IJTJTUIFQFSJPEPGUIFXBWF5IFi)VNBO8BUFS8BWFwIBTB
QFSJPEPGPOFPSUXPTFDPOET)FDIBOHFTUIFTIBQFPGUIF
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[FSPTIBQFCZTMJEJOHPGBOFOEoNJEEMFUPUPQBOENPWJOH
UPUIFGSPOU5IJTJTUIFXBWFMFOHUIPGUIFXBWF
5IJTJTUIFUSBEJUJPOBMXBZUPESBXPOFDZDMFPGBXBWFBTP
XBWFMFOHUI
-BCTJNVMBUJPO5IFUFBDIFSiåSFTwUIBUSPXBOENPWFTUP
BOPUIFSSPXUIBUIBTOPUEPOFiUIFXBWFw5IFZQSBDUJDFXJUI
UIFCBTLFUCBMMiESPQwXJUIBQFBLNPWJOHPOFEFTLBUBUJN
5IFUFBDIFSXSJUFTEPXO%FåOJUJPOPOFDZDMFNJEUPUPQ
UPNJEUPCPUUPNUPNJE0OFQFSJPEPOFDZDMF5IFQFSJPE
JTVTVBMMZXSJUUFOUBTQJTBMSFBEZUBLFOXJUINPNFOUVN
%FåOJUJPO'SFRVFODZOVNCFSPGQFSJPETQFSTFDPOE
0VSiIVNBOXBWFwJTPOFDZDMFQFSTFDPOEPSQFSIBQTPOF
DZDMFQFSTFDPOETJGUIFUJNFXBTTFDPOET
'SFRVFODZJTUSBEJUJPOBMMZSFQSFTFOUFECZTNBMMf$BQ
SFTFSWFEGPSGPSDF*UTGSFRVFODZJT
cycle
f=
sec
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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 = f5IJTJTB
TQFDJBMFRVBUJPOUIBUNVTUCFSFNFNCFSFE
5IFJOTUSVDUPSXSJUFTEPXOTQFFETPGPUIFSXBWFT
5IFTQFFEPGTPVOEJTNT
5IFQIZTJDTPGUTVOBNJTBOEPGXBWFTJOXBUFSJTDPNQMJ
JOHFOFSBM8FPGGFSBTJNQMFWFSTJPOIFSF*OEFFQXBUFS
UIFXBUFSNPMFDVMFTPTDJMMBUFBTUIFXBWFTDPNFUISPV
DZDMFT*GUIFXBUFSJTTIBMMPXUIFCPUUPNQBSUPGUIFDZD
ESBHTPOUIF&BSUIBOETMPXTJUTPUIBUUIFXBWFFMPOHBU
&WFOUVBMMZUIFCPUUPNTMPXTNPSFUIBOUIFUPQBOEUIF
CSFBLTXJUIXIJUFUPQT
5IFTQFFEPGXBWFTJOXBUFSEFQFOETPOEFQUIGPSNBOZ
SFBTPOT8BUFSNPMFDVMFTTUJDLUPFBDIPUIFSJOCFBETPO
BTVSGBDFBOEFWFOJOMJRVJEEFQUIT5IJTBGGFDUTUIFXBW
QBTTJOHUISPVHIUIFXBUFSNFEJVN5IFEFQUIPGUIFXBUFS
NFEJVNBGGFDUTUIFTQFFEPGBXBUFSXBWF
The equation is: v = gd
5IJTFRVBUJPOJTOPUBHSFBUMBXPGQIZTJDT*UJTEFSJWFE
CZBOBMZTJTVTJOH/FXUPOJBOQSJODJQMFTBOEBQQMJFT
MJNJUFEDBTFPGXBUFSXBWFT*UTIPVMEOPUCFNFNPSJTFE
"DUJWJUZ2VBMJUBUJWFMPPLJOHBUUIFFRVBUJPOv = gd
*OTUVEFOUHSPVQTNBLFQSFEJDUJPOTBCPVUUIFSFMBUJW
PGXBUFSXBWFTJOEFFQPDFBOTJOTNBMMQPOETPSSJWFS
BQPPMPSUIJOMBZFSTJOBQMBUF
5IFJOTUSVDUPSDPMMFDUTJEFBTGSPNHSPVQTBCPVUXIBU
UIJOLXJMMIBQQFOUPUIFWFMPDJUZPGXBUFSXBWFT4PNFN
PGGFSDBMDVMBUJPOT3FDPSEUIFN
"DUJWJUZ#PBSEDBMDVMBUJPO
5IFEFQUIPGUIFPDFBOJTBCPVUN8IBUJTUIFTQFFE
PGBUTVOBNJBHJBOUPDFBOXBWFDBVTFECZBOFBSUIRVBL
the open?
*UJTBCPVULQI5IJTJTBTGBTUBTBKFUQMBOF*UTMPXT
XIFOJUBQQSPBDIFTMBOEBTUIFCPUUPNFODPVOUFSTGSJD
XJUIUIFMBOE*UTXBWFMFOHUIJTWFSZMPOHoBCPVULNPS
MPOHFS
8IBUJTUIFGSFRVFODZPGBHSPVQPGUTVOBNJXBWFT
"DUJWJUZRVBMJUBUJWFJOWFTUJHBUJPOPVUTJEFDMBTT
/
Grade 9
/
149
Grade 9: Physics syllabus
Competencies
Contents
Suggested activities
"TLTUVEFOUTUPFYQMPSFBUIPNFPCTFSWBUJPOTPGUIFTQF
XBWFT8IBUIBQQFOTUPXBWFTBTUIFZDPNFBTIPSF 8IBU
PCTFSWBUJPOTDBOZPVNBLFPGXBWFTNBEFJOBTIBMMPXBS
BOEXBWFTNBEFJOEFFQFSXBUFS $PMMFDUPCTFSWBUJPOT
UIFZåUUIFFRVBUJPO *GOPUSFQFBUUIFFYQFSJNFOUT
%FNP4UVEFOUTQVUPVUUIFJSIBOET&BDIIBOEJTBXBUFS
NPMFDVMF5IFUFBDIFSiESPQTwBUFOOJTCBMMPOPOFFOE
4UVEFOUTIBOETNPWFTJNVMBUJOHUIFXBWFBUTQFFEPGPO
EFTLQFSTFDPOE
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height between the middle point and the highest or lowest
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which way?
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150
Grade 9
Grade 9: Physics syllabus
Competencies
Contents
Suggested activities
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Is there a total displacement? Students must appreciate that
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Grade 9
151
Grade 9: Physics syllabus
Competencies
Contents
Suggested activities
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there systematic error? How big is it?
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Or is it the same?
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Glass or water are denser than air, so light is slower in these
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Classroom assessments
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Speed = f
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152
Grade 9
Grade 9: Physics syllabus
Competencies
Contents
Suggested activities
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m/s
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Model with a rope and a chalk how sound, light or water get
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Assessment
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Students at minimum requirement level
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Students below minimum requirement level
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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