Students read 9.2 Musical Instruments in How Things Work the Physics of Everyday Life and watched the following videos before class.

For the lab I found this handout for Lab 8: Waves & Sound on the University of Oregon Physics 101. We got through the first couple of labs in the handout. Students took a large slinky, or coil spring and played around… I mean practiced making wave pulses and standing waves.

Then they stretched out the slinky to a certain distance (2 meters in this case) and timed how long it took a wave pulse to travel down the slinky and back (4 meters total). Knowing the distance traveled and the time it took, they could calculate the wave speed, v = distance/time. The second experiment had them set up a standing wave like in the photo below and calculate the wavespeed by using the wavelength and the frequency of the wave (number of oscillations per second). In the photo below the wavelength is 2 meters, the same as the distance between the end points. To find the frequency they timed how long it took for 10 complete oscillations of the standing wave (moving from the position as shown in the photo, to the opposite side and back to the same position). From that time they could find the time for one oscillation, T, and the frequency is just one over the period, f = 1/T. The wave speed is equal to the wavelength times the frequency. They found the wave speed was the same for the wave pulse and the standing wave.

They then stretched the slinky or coil spring to increase its length and the tension in the spring and repeated the standing wave measurement and found the wave velocity increased with increased tension. The experiment was repeated once more, using half the slinky and the original distance so the tension would be roughly the same as when stretching the slinky twice as far and they got the same higher wave speed as expected.