Physics of Sound II

Today we learned how sounds create vibrations. We had two different tuning forks tuned to different frequencies, one high, and one low. The students listened to the different sounds, or frequencies, with their ears. They felt the tuning fork's vibrations on their fingernails and skin. They struck the tuning fork on a wooden block and placed them in cups of water. They noted the tuning fork with the higher frequency caused the water to splash out of the cup, where the lower tuned fork did not. The decided it was because the higher the frequency, the faster the vibration, the faster the vibration, the more energy it expended cause the water be stirred up more and therefore splashing out. They also tested the vibration's effect on a ping pong ball suspended from a string. Again, the tuning fork with the higher frequency made a bigger impact than the lower frequency. Above, Tanner tests the ping pong ball.

They also, among other activities, learned about a frequency generator. We had one (shown in the picture) that was able to sweep through a set of high to low frequencies. After they felt the vibration on the speaker, we placed dried beans on the speaker and by adjusting the frequency, the students observed the beans bouncing around. By slowly sweeping through the frequency range of the generator, the student found specific frequencies that cause the beans to jump right off the speaker. Below, Javier, adjusts the tone generator.