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Re: [Phys-l] a simple toy



Intriguing! I'll have to try this. What size balloon did you use? My
kids have somewhat cylindrical ballons that are perhaps 20 cm long and
perhaps 8-10 cm in diameter. But from your description I think you are
using more nearly spherical balloons -- that might be better.

Ken Caviness,
Physics @ Southern

-----Original Message-----
From: phys-l-bounces@carnot.physics.buffalo.edu
[mailto:phys-l-bounces@carnot.physics.buffalo.edu] On Behalf Of Leigh
Palmer
Sent: Wednesday, August 30, 2006 4:29 PM
To: phys-l@carnot.physics.buffalo.edu
Subject: [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
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