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[Phys-l] a simple toy



I just finished inflating a dozen balloons for my granddaughter's birthday party. As is my custom, I put a quarter (coin) into each balloon. Even a three-year-old will quickly discover that the quarter can be made to roll around on the inside of the balloon, like a bicyclist on a velodrome. If, after starting the orbit in a near horizontal plane, one holds the balloon still, the orbit will decay slowly. It makes a lovely, soft whirring sound, too due to the milled edge.

There are lots of questions that can be evoked by observing this toy, and there is room for experiment as well. Different coins can be used. A Sacajawaya takes more than a minute to decay, and a two pound coin almost as long. (The two pound coin has another interesting optical feature, as some of you will know.) The sounds are very different from the quarter, the Sacajawaya being almost silent. Try also the polygonal Canadian dollar and one cent coins. I used to use this toy as a VFO for a lecture resonance demonstration.

Anyway, if you have never played with this toy let me urge you to do so.

Leigh