I’ve taught the physics and biology (hearing/echolocation) of sound MANY times over the last 8 years so for class this week I dusted off an whole slide show on sound waves and showed a bunch of youtube videos. The first video showed a clip from the Time Warp TV show on how to break wine glasses with sound waves – they took a slow motion video of the glass vibrating at its natural frequency and eventually cracking.

I also showed a MinutePhysics video on the Tacoma Narrows Bridge failure.

Here’s an article that explains why the bridge failed.

And lastly a nice explanation of the Doppler Effect.

I didn’t show this in class, but here are clips from Big Bang Theory when Sheldon decided to be the Doppler Effect for Halloween.

For the laboratory portion of class the students took a very long spiral spring laid it on a hard floor (not carpet) and sent wave pulses down the spring.

They used the video physics app to record the motion and determine the speed of the wave pulse at different tensions of the coil.  As the tension increases, the speed of the wave pulses increases.  I also had a set of tuning forks out and an ipad app, SpectroPro, that used the ipad microphone to pick up the sound waves from the tuning fork (or other sound sources) and showed the frequency of the sound.

We also played with obleck (1 part water to 1.5 parts cornstarch) on a foil pan over a subwoofer – I didn’t get very good movies of it.  But the Slow Mo Guys on youtube did a great job.

And lastly, I recommended that the students download the free Sound Uncovered app by the Exploratorium.  It has a variety of activities to do with sound, including testing your own hearing range.  We found a couple of students in the class could hear frequencies quite a bit higher than the rest of us!

 

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