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Kami Export - Julio jimenez - Waves Gizmo
University of Maryland Global Campus
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PhysicsPreview text
Name: Date:
Student Exploration: Waves
Vocabulary: amplitude, compression, crest, frequency, linear mass density, longitudinal wave, medium, period, power, rarefaction, transverse wave, trough, wave, wavelength, wave speed
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
A buoy is anchored to the ocean floor. A large wave approaches the buoy. How will the buoy move as the wave goes by?
The two images show side views of ocean waves. How are the two sets of waves different?
Gizmo Warm-up Ocean swells are an example of waves. In the Waves Gizmo, you will observe wave motion on a model of a spring. The hand can move the spring up and down or back and forth.
To begin, check that the Type of wave is Transverse , Amplitude is 20 cm, Frequency is 0 Hz, Tension is 3 N, and Density is 1 kg/m. (Note: In this Gizmo, “density” refers to the linear mass density , or mass per unit length. It is measured in units of kilograms per meter.)
- Click Play ( ). How would you describe the motion of a transverse wave?
Click Pause ( ). Notice the crests (high points) and troughs (low points) of the wave.
- Click Reset ( ). Choose the Longitudinal wave and increase the Amplitude to 20 cm.
Click Play. How would you describe the motion of a longitudinal wave?
Click Pause. Notice the compressions in the wave where the coils of the spring model are
close together and the rarefactions where the coils are spread apart.
Activity A: Measuring waves
Get the Gizmo ready:
x Click Reset. Select Transverse waves. x Set Amplitude to 20 cm, Frequency to 1 Hz, Tension to 2 N, and Density to 2 kg/m.
Question: How do we measure and describe waves?
- Observe: Click Play. Observe the motions of the hand and of the green dot in the middle.
A. What is the motion of the hand?
B. Turn off the Lights on checkbox and observe the green dot. What is the motion of
the green dot?
C. Follow the motion of a single crest of the wave. How does the crest move?
In a transverse wave , the motion of the medium (what the wave moves through—in this case, the spring) is perpendicular to the direction of the wave. So, each point of the spring moves up and down as the wave travels from left to right.
- Measure: With the lights on, click Pause. Turn on Show rulers.
A. Use the horizontal ruler to measure the horizontal distance between two crests. What
is this distance? This is the wavelength of the wave.
B. What is the distance between the two troughs?
The wavelength can be found by measuring the distance between two successive crests, two successive troughs, or any two equivalent points on the wave.
C. Click Reset. Set the Density to 1 kg/m. Click Play , and then Pause. What is the
wavelength of this wave?
- Measure: Click Reset. The amplitude of a transverse wave is the maximum distance a point on the wave is displaced, or moved, from its resting position. Turn off the lights. Click Play , and then click Pause. Use the vertical ruler to measure the height of the green trace, showing how far the green dot moved up and down.
A. What is the height of the green trace?
B. The wave’s amplitude is equal to half of this height. What is the amplitude?
(Activity A continued on next page)
Activity B:
Wave dynamics
Get the Gizmo ready:
x Click Reset. Check that Transverse is selected. x Set Amplitude to 20 cm, Frequency to 0 Hz, Tension to 3 N, and Density to 1 kg/m.
Question: What factors affect the wavelength, speed, and power of waves?
- Record: The speed of a wave is the distance a wave pulse travels per second. The wave
speed is displayed below the spring. Click Play. What is the wave speed?
- Experiment: The wavelength and speed of a wave can be influenced by many factors. Adjust the amplitude, frequency, tension, and density as described in the table below. Then report whether this causes the wavelength and wave speed to increase or decrease. Return each variable to its original value after each experiment.
Adjustment Effect on wavelength Effect on wave speed Increase amplitude
Increase frequency Increase tension Increase density
- Analyze: Click Reset. Set the Frequency to 0 Hz, Tension to 2 N, and Density to 2. kg/m. Click Play , and then click Pause. Turn on Show rulers.
A. What is the wavelength?
B. What is the wave speed?
C. How are the wavelength, frequency, and wave speed related?
In general, the wave speed ( v ) can be calculated from the frequency ( f ) and wavelength ( λ ) using the formula v = f • λ.
D. What is the wavelength of a wave with f = 0 Hz and v = 154 cm/s?
To check, set Frequency to 0 Hz, Tension to 2 N, and Density to 1 kg/m.
E. Change the Density to 1 kg/m, and click Play. Based on the wave speed, what do
you expect the wavelength to be? Measure the wavelength to check.
(Activity B continued on next page)
Activity B (continued from previous page)
- Gather data: Click Reset , and turn off Show rulers. The power of a wave is the amount of energy it transmits each second. The power of the wave is displayed below the spring when Play is pressed. Record the wave power for each of the settings below.
Amplitude Frequency Tension Density Power 20 cm 0 Hz 2 N 1 kg/m
40 cm 0 Hz 2 N 1 kg/m
20 cm 0 Hz 2 N 1 kg/m 20 cm 1 Hz 2 N 1 kg/m
20 cm 0 Hz 2 N 1 kg/m
20 cm 0 Hz 4 N 1 kg/m
20 cm 0 Hz 2 N 0 kg/m 20 cm 0 Hz 2 N 1 kg/m
Which factors increased the power of the wave?
- Compare: Click Reset. Select Longitudinal waves. Set Amplitude to 20 cm, Frequency to 0 Hz, Tension to 2 N, and Density to 1 kg/m. Click Play.
A. What is the power of this longitudinal wave?
B. Compare this power to the power of a transverse wave with the same settings. Does
changing the type of wave affect its power?
Apply: Sound waves are longitudinal waves that can travel through air. Would you expect sound waves to travel faster through a low-density gas (such as helium) or a higher-density gas such as carbon dioxide? Justify your answer based on what you have learned.
Apply: As ocean waves approach the shore, friction with the ocean bottom causes them to slow down. If the frequency is the same, how will this affect the wavelength of the waves?
Kami Export - Julio jimenez - Waves Gizmo
University: University of Maryland Global Campus
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