Wave on a String
***LINK TO SIMULATION https://phet.colorado.edu/sims/html/wave-on-a-string/latest/wave-on-a-string_en.html *** How can we determine the speed of the wave? Come up with two ways (i.e., each with their own equation) to measure the speed of the wave. Do you predict that both methods will give the same result? The first method we will test for measuring the speed of the wave is speed = distance/time, i.e., v = d/t. Select Oscillate in the green box and select No End in the other green box. Select Rulers and Timer in the wide green box. Instead of continuous motion, single-step the wave by selecting the smaller of the two blue imagesThe advance button on the physics simulation.. Each time you select that image the wave advances. Select it many times (around 21 times) so that the peak of the wave is centered on 0 cm of the ruler. Now select the triangle to activate the timer. The timer will advance with each step of the wave. Single-step the wave many times until the peak of the wave has moved from 0cm to 3cm and record the time on the timer (it will be in units of seconds). Divide the distance traveled (3cm) by the time shown on the timer and record the result as the speed of the wave. Did you come up with a second way to measure the speed of the wave? You can use the fundamental wave equation, frequency x wavelength = speed, i.e. f λ = v Move the ruler so that you can measure the separation between two wave peaks (in cm). That will be the wavelength. Read the frequency from the frequency meter in the wide green box. Multiply the wavelength and frequency to calculate the speed. How did the two estimates of speed (the first using v = d/t and the second using f λ = v) compare? If you find a large discrepancy, please retry the measurements. If you find a small discrepancy, please explain it in your experiment report. In the short video clip (https://youtu.be/T9QwiBFN9gI), a stone is tossed into a pond, and ripples are seen. What moves from one side of the pond to the other, water or energy? How about the vertical motion? Is it the water (i.e., medium) that moves up and down or the wave? To explore this, turn off the Timer and select Slow Motion. Select the main image (Pause/Play button) The stop/play button on the physics simulation. to start continuous wave motion and move the vertical ruler so it is adjacent to the 2nd green bead. Do you notice that the green bead (representing a portion of the medium) just moves up and down while the wave crest moves to the right? You can single-step the wave motion as you did in Activity 2 if it helps to see this. What do you conclude moves vertically and what moves horizontally in the water ripple? Use the simulation to make one observation about wave motion that you can't yet explain. One possibility is to select Pulse in the green box and Fixed End in the other green box. Then, select the triangle wave image The triangular wave pulse button on the physics simulation. on the wave generator and watch as the triangular wave pulse propagates to the right and is reflected. How does the reflected wave pulse compare to the original wave pulse?

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