Re: another gedankenapparat

[John Mallinckrodt <ajm@CSUPOMONA.EDU>]

Since nobody else seems to have commented upon it, I'd like to say
that I enjoyed this contribution from Mark.  I guess we could call
this "heat capacity at constant angular momentum." (?)  I think it
serves as a nice example to help students understand the usefulness
of C_p and C_v, to illustrate how the unfortunately named quantity,
"heat capacity," is really about the relationship between changes in
internal energy and temperature, and to demonstrate that it
necessarily depends on the constraints placed on a system.

> 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.

--
John Mallinckrodt        mailto:ajm@csupomona.edu
Cal Poly Pomona          http://www.csupomona.edu/~ajm