4 Elaborate_ Gizmos Waves

A buoy is anchored to the ocean floor. A large wave approaches the buoy. How will the buoy move as the wave goes by? I think the buoy doesn’t move but rather goes through it because it is anchored to the ocean floor. 2. The two images show side views of ocean waves. How are the two sets of waves different? The two sets of waves look different because of their crests, wavelengths, troughs, amplitudes, and the resting point. 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 20.0 cm, Frequency is 0.75 Hz, Tension is 3.0 N, and Density is 1.0 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.) 1. 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. The motion of a transverse wave is that the spring is moving up and down. Both the crests and troughs are the same. Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved This study source was downloaded by from CourseH on :21:49 GMT -05:00 2. Click Reset ( ). Choose the Longitudinal wave and increase the Amplitude to 20.0 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. The motion of a longitudinal wave is moving back and forth, as the wave moves left to right, making rarefactions and compressions. Activity A: Measuring waves Get the Gizmo ready: ● Click Reset. Select Transverse waves. ● Set Amplitude to 20.0 cm, Frequency to 1.0 Hz, Tension to 2.0 N, and Density to 2.0 kg/m. Question: How do we measure and describe waves? 1. 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? The motion of the hand is transferring energy by moving the hand up and down. B. Turn off the Lights on the checkbox and observe the green dot. What is the motion of the green dot? The motion of the green dot is moving up and down in a straight line. C. Follow the motion of a single crest of the wave. How does the crest move? The crest is moving from left to right. 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. 2. 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? 100 cm. This is the wavelength of the wave. B. What is the distance between the two troughs? Also, 100 cm. 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 1.0 kg/m. Click Play, and then Pause. What is the wavelength of this wave? 140 cm. 3. 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 Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved This study source was downloaded by from CourseH on :21:49 GMT -05:00 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? 40 cm. B. The wave’s amplitude is equal to half of this height. What is the amplitude? 20 cm. 4. Observe: Click Reset. Select Lights on and turn off Show rulers. Select Longitudinal waves. Check that the Amplitude is 10.0 cm, the Frequency is 1.00 Hz, and the Tension is 2.0 N. Set the Density to 1.0 kg/m, and click Play. A. What is the motion of the hand? The motion of the hand is moving back and forth. B. Turn the lights off. What is the motion of the green dot? The motion of the wave is moving left to right in a straight line. C. Follow the motion of a single compression of the wave. How does the compression move? The compression moves from the left to the right. In a longitudinal wave, the motion of the medium is parallel to the direction of the wave. So, each point of the spring moves back and forth as the wave is transmitted from left to right. 5. Measure: With the lights on, click Pause. Turn on Show rulers. A. The wavelength of a longitudinal wave is equal to the distance between two successive compressions (or rarefactions). What is this distance? 140 cm. B. How does this compare to the wavelength of the comparable transverse wave? (See your answer to question 2C.) The wavelength of the transverse wave and the distance between rarefactions are the exact same. 6. Measure: Click Reset. The amplitude of a longitudinal wave is equal to the distance a point on the wave is displaced from its resting position. Turn off the lights. Click Play, and then click Pause. Use the horizontal ruler to measure the width of the green trace. A. What is the width of the green trace? 20 cm. B. The wave’s amplitude is equal to half of this height. What is the amplitude? 10 cm. 7. Calculate: Click Reset. Select Transverse waves. Select Lights on and Show grid and turn off Show rulers. Set the Frequency to 0.50 Hz. A single cycle is the time it takes the hand to move up, move down, and then back up to the starting position. Click Play, and then click Pause after exactly one cycle. (This may take a few tries.)