Workout: Wave pulses

Read

the webpages Wave pulses, Propagating a wave pulse -- the math, and Wave speed.

Launch

the PhET simulation, Waves on a string.

Set up

Click on the wrench and move it up and down a few times to see how it works. Then set the switches to "No end" (in the upper right) and "Pulse" (in the upper left). Click on "Rulers" (in the lower right) and set the damping to 0. Your screen should look like that shown below. (It might be useful to set the sim to "Slow Motion" to better see what is going on.)

Answer these questions

1. Press the green button on the device that generates the pulse and observe what happens. The green box at the bottom gives a number for the "Pulse Width" but it's a time, not a width (a distance). What does this number mean?
2. What is the actual width in space of the pulse? (Hint: Pause the sim and use the ruler to measure it.)
3. From this data, calculate the speed with which the pulse is travelling down the chain.
4. "Tell the story" of what's happening with the generation of the pulse in a way that makes it clear why you did the calculation you did to get the speed of travel of the pulse.

Joe Redish, Spring 2017