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another gedankenapparat

At 17:43 22/12/03 -0500, Chuck Britton wrote:
Excellent gedankenapparat, but I'm still not seeing the angular
momentum conservation thing....

Thanks for asking the question - me too.

Meanwhile, here's another contrivance to ponder. It's not as interesting as
the gyro-driven generator, but I've had it on my mind for some time:

A hot metal disk spinning on a frictionless bearing in a vacuum. It cools
(by radiation I suppose) and contracts as a result of cooling. The diameter
decreases and it spins up, conserving angular momentum. Work is done by
interatomic forces acting in the radial direction, and the kinetic energy
of the disk increases. Am I correct in supposing that the disk has a
smaller heat capacity when spinning than when not? Rather like a gas has
different c's according to what you do with p and V while heating or
cooling it.

Mark

Mark Sylvester
UWCAd
Duino Trieste Italy