An aluminum rod, supported in the middle, rings for a long time in its longitudinal mode.
What it shows:
Longitudinal standing waves in solids.
How it works:
A metal rod is not unlike an organ pipe with both ends open. Holding it exactly in the middle will force the simplest, or fundamental, mode of vibration -- the ends will be free to vibrate maximally and the center will be a node. The fundamental frequency happens to be 2.26 kHz. As with a pipe open at both ends , the rod will vibrate at all the odd as well as even...
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