Science SCI.IV.4.5 Grade: 7 Strand IV: Using Scientific Knowledge in Physical Science Standard 4: Waves and Vibrations ­ All students will measure and describe vibrations and waves. Benchmark 5: Describe the motion of vibrating objects. Constructing and Reflecting: SCI.I.1.1 ­ Generate scientific questions about the world based on observation.
· Construct questions for each of the investigations suggested below guiding the design of the investigation. SCI.I.1.2 ­ Design and conduct scientific investigations. SCI.I.1.3 ­ Use tools and equipment appropriate to scientific investigations. SCI.II.1.2 ­ Describe limitations in personal knowledge. Vocabulary / Key Concepts
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period
frequency
amplitude Context Vibrating or oscillating objects:
· weights on springs
· vocal cords
· tuning forks
· guitar strings
Knowledge and Skills Resources Coloma Resources: Video – Science Court Sound & Light – Chapter 1 Students will describe the motion of vibrating objects using the following terms:
· Period ­ time it takes for one complete swing of Other Resources
a pendulum (back and forth) or one vibration.
· Physical Science Activity Manual –book · Frequency ­ the number of periods or written by a group of teachers using the vibrations for a given time
learning cycle and 34 activities to teach · Amplitude ­ the distance the pendulum is physical science. Excellent resource!
“pulled out” from at rest. ·
With a tuning fork, one vibration of the tongs represents the period. The more vibrations or periods the tines of the tuning fork make, during a certain time, the higher the frequency. The harder ·
the tuning fork is struck the larger the amplitude will be. This can be heard by an increase in loudness or volume. How Satellites See– excellent interactive learning! – from UC Berkeley Center for Science Education
ExploreLearning – Waves, sound, and light – excellent site – free preview, but requires subscription.
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DiscoverySchool – The Phenomenon of Sound – Waves
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The Exploratorium – Science Snacks about Waves
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Michigan Teacher Network Resources
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Smile Physics Program – Waves, Sound and Optics ­ Illinois Institute of Technology
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Science Explosion: Waves and Vibrations
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Bill Nye: Eyeball, Light/Color, Light/Optics, Sound, Waves Videoconferences Available For more information, see www.remc11.k12.mi.us/dl or call Janine Lim 471­7725x101 or email jlim@remc11.k12.mi.us IV.4.MS.5 Describe motion of vibrating objects Amazing Sound from National Science Center 7 th Grade Science Curriculum Technology Resources IV.4.MS.5 Vernier probes available: Microphone
Instruction Assessment Coloma Assessment Focus Question: How is the motion of objects related Do the Wave (attached) to sound and frequency? Period, Frequency & Amplitude (attached) Relationship of Frequency, Wavelength, and Instruction I Speed (attached) Arrange students in groups of three. Have student’s place a Rubric long spring tightly between two posts i.e. table / chair legs 6 – Table (distance between posts depends on length of spring). In 10 – Summing up groups of three, have one student time for one minute, while another student hits one post with a hammer in a steady 4 – Going Further manner. The third student should count the number of hits 20 – Total Points with a hammer and describe the sound made. At this point describe frequency. (In this case, frequency is the number of hits by the hammer) Relate this flow of waves down the spring to the side to side motion of a tuning fork or your vocal cords. Then have the students vary the number of hits by the hammer. What happens to the sound (pitch) and the frequency of the vibration? NOTE: One hit by the hammer is one cycle or period. Next have the student vary the amount of energy applied to the hammer by hitting “softer” and “harder”. Have the students describe the difference in the sound made and in relation to its volume and relate it to the amplitude of the waves made by the spring. Instruction II Optional Assessment Give the students pictures of sound waves produced by an oscilloscope or diagrams of sound waves that represent different sounds. Have students write responses to the following questions on frequency, period and amplitude.
· Which one did the objects with the longest period produce? How do you know?
· Which wave has the greatest amplitude? How do you know?
· Which one was produced by the object with the highest frequency? How do you know?
· Which one produces the highest sound? Why? Focus Question: How is the motion of vibrating objects related to sound? Students will work in small groups to design and conduct an investigation that answers the Focus Question. Each student will write a hypothesis before beginning the investigation. Then students will follow these procedures: 1. Stretch a rubber band tightly around three nails in a board. 2. Hang several small strips of paper, creased in half, over one section of the rubber band. 3. Pluck the section. 4. Observe how the paper strips move. 5. Measure how long a guitar string vibrates after it can no longer be heard. Each student will write a lab report describing the investigation. Extension: Give students various toys that make sound. Have them investigate the differences in pitch and loudness and how they can be changed. Similarly, strips can be placed over the different strings of string instruments. (Give students rubric before activity.) Scoring Rubric Criteria: Correctness of identification – Apprentice ­ Identifies one picture correctly. Basic ­ Identifies two pictures correctly. Meets ­ Identifies three pictures correctly. Exceeds ­ Identifies four pictures correctly. Criteria: Accuracy of explanation ­ Apprentice ­ Writes one correct conclusion based on incorrect or no information. Basic ­ Writes two correct conclusions based on some correct information. Meets ­ Writes three to four correct conclusions based on some correct information. Exceeds ­ Writes five to six correct conclusions based on all correct information.
Teacher Notes:
· “Vibrations in materials set up wavelike disturbances that spread away from the source. Sound and earthquake waves are examples. These and other waves move at different speeds in different materials” (BSL). These waves transfer energy by setting the material (medium) in vibrating motion. The strength of the motion is in the amplitude of the wave; the speed of vibration is its frequency. Focus Questions
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What is a vibration?
How do vibrating objects move?
How do mechanical waves transfer energy? Notes The state benchmarks are very deliberately constructed to take students through these topics sequentially and developmentally. For example, students do not talk about sound and light as waves until the high school benchmarks – they only look at vibrating objects and mechanical waves such as those in slinkies or on water in middle school. They recognize sound as produced by vibrations at the elementary level; they study the motion of vibrating objects at the middle school level; and they apply the concepts of vibrations to sounds at the high school level.
Hypothesizing Read through the procedure. Make a hypothesis about how the speed of moving the rope up and down affects the frequency. You will need:
· Goggles
· Meterstick
· Piece of colored yarn
· Graph paper
· Rope about 5 m long
1. Tie the piece of yarn to the rope about 1 m from the end. 2. Tie the end of the rope furthest from the yarn to an immovable object, such as a table leg. pull the rope so that it does not sag. 3. Make waves in the rope by rapidly moving the free end up and down. Continue to move the rope at a steady rate. Observe the crests and troughs of the waves. Be prepared to show these to your teacher or another student. 4. Continue making waves by moving the rope at a constant rate. Count the number of waves that you produce during a period of 30 s by observing the piece of yarn. Record this value. (Speed A) 5. Predict what will happen to the frequency if you slow, the rate of movement. Slow the movement down and count the number of waves that you produced in 30 s while maintaining this constant slower rate. Record this value. ______________(Speed B) 6. Speed up the rate of Step 5. Maintain this constant rate for 30 s. Record this value. ________________(Speed C) Data Table Speed A /30 s = Hertz (waves per 1 s) Speed B /30 s = Hertz (waves per 1 s) Speed C /30 s = Hertz (waves per 1 s) Summing Up/Sharing Results What happened to the frequency as you increased the speed of the rope? Make a bar graph of the results, comparing Speeds A, B, and C. Compare your predictions with your results. Going Further How would the experiment have been different if you had attempted it under water? Design an experiment where you could do this. Do the Wave! It would be difficult to find a place on Earth that is not affected by waves in some way. From the gentle lapping of waves along a lakeshore to the waves of sunlight striking a sidewalk, waves are everywhere. They even reach below Earth's surface in the form of earthquakes. Earthquakes produce three kinds of seismic waves: primary, secondary, and surface waves. Surface waves do the most damage. Even after the earthquake has taken place, a tsunami (a seismic sea wave) can cause severe damage thousands of miles away, engulfing entire coastal towns. If you've ever dropped a pebble in a puddle of water and watched the ripples fan outward, you've observed the shape of one kind of wave. The high part or hill of a wave is the crest. The low part or valley of a wave is the trough. The wavelength is the distance between two similar points on successive waves. The number of wavelengths that pass a point in one second is the frequency of the wave. Frequency can be found using the following equation. Frequency is measured in Hertz (Hz). Frequency = Number of wavelengths/l s Getting Started In this activity you will observe waves. You will calculate the frequency of a wave using a rope, and determine how the speed of moving the rope up and down affects the frequency. CAUTION: Wear eye protection when using the rope in this activity.
Resource 7:7c, page 2 DATA RECORD Length of String Amplitude Frequency Period P = F + T QUESTIONS: 1. Compare amplitude with frequency. 2. Compare amplitude with period. 3. Compare frequency with period. 4. How does the length of the string affect frequency? 5. How does the length of the string affect period? 6. How does a pendulum compare to a wave? Compare the properties of a wave with the movements of a pendulum.
Resource 7:7c, page 1 PURPOSE: To investigate the relationships between the properties of a wave (amplitude, frequency, and period) using the movements of a pendulum. MATERIALS: (For groups of 2)
· 1 90 cm piece of string
· 1 metal washer
· 5 cm piece of masking tape
· 1 ruler
· 1 meter stick
· timer that indicates seconds BACKGROUND: Amplitude is the distance between the position of rest and the highest position in the arc. Frequency refers to the number of times an object moves back and forth in a given amount of time. A Period is the time it takes for one complete swing back and forth. Period = frequency + time in seconds PROCEDURES: 1. Create a pendulum by tying a washer to one end of the string. 2. Tape the other end of the string to the ruler so that 80 cm of string hang down. 3. Tape the ruler to a table so the pendulum extends about 5 cm from the edge. 4. Pull the end of the pendulum back about 60 cm. Use the meter stick to measure the distance (amplitude). Let go, and record how many times (frequency) the pendulum makes a complete back and forth swing in one minute. 5. Repeat Step 4 pulling the pendulum back 30 cm. 6. Repeat Step 4 pulling the pendulum back 15 cm. 7. Shorten the string to 40 cm and repeat STEP 4. 8. Shorten the string to 20 cm and repeat STEP 4. 9. Shorten the string to 10 cm and repeat STEP 4.
Resource 7:7d PURPOSE: To discover how a wave's frequency, wavelength and speed are related. MATERIALS: Clear dish or glass pan approximately 30 square Strips of plastic foam tape Water 1 pencil Overhead light 1 piece of blank white paper 1 ruler 1 piece of drawing paper DIRECTIONS: 1. Tape strips of plastic foam to the inner edges of the dish. Pour about 3 cm of water in the dish. 2. Set the dish on the blank piece of white paper under an overhead light source. 3. Tap the water with the end of the pencil and observe the wave created by looking at the paper. 4. Draw the shape of the wave. The crests of the wave will appear as bright lines and the troughs appear as darker lines. 5. Compare the speed of the wave in all directions. 6. Tap the water again making a series of waves. Increase the frequency by tapping the water faster. 7. Observe the change in wavelength. 8. Draw an example of a low and high frequency wave. QUESTIONS: 1. What effect does increasing the frequency have on wavelength of the waves produced? 2. What is the relationship between wavelength and frequency?