1. I am a mathematician trying to understand a physics experiment where an aluminum rod is held in the middle and struck with a mallet. The rod is then placed next to a microphone, the sound recorded and the frequency determined using Audacity. Working backwards, one determines the speed of sound in aluminum.(adsbygoogle = window.adsbygoogle || []).push({});

2. I made this applet using GeoGebra: http://geogebrawiki.wikispaces.com/Speed+of+Sound

Most important question:Do I have it right?

3. Questions - Believe me, I have spent over 10 days researching these questions so any answers here would be GREATLY appreciated.

(a) Is there only the one standing wave with this amplitude or do we also get the upside down one (it seemed like it would cancel the one I graphed so I took it off, but I looked at other pictures and they have both).

(b) Are there other standing waves of different amplitudes? What does amplitude mean here?

(c) Is the sound wave 2D or does it wrap itself around the rod (i.e. the rod is 3D, is the wave only 2D and if so on what plane)?

(d) Clearly the length of the wave gets longer as more nodes appear. However the time from one end of the rod to the other is the same (speed of sound). Does the fact that a point on the wave travels faster have any physical significance? (As I understand frequency, it is the number of times a point peaks per second. But does the actual "linear speed" of the point mean anything other than relating frequency and amplitude?)

Thank-you!

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# Standing waves, aluminium, speed of sound

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