Re: Thermal Energy - thermalization of rotational energy

[John Mallinckrodt <ajmallinckro@CSUPOMONA.EDU>]

On Wed, 6 Mar 2002, Bob Sciamanda wrote:

> A simpler scenario would have two wheels spinning in opposite senses, so
> that there is zero net ang mom. Then 100% of the spinning wheels'
> rotational energy can be thermalized by braking both wheels, with zero
> residual rotational energy of anything.

Granted.  Nevertheless ...

I know that this is to some extent semantics, but I really would
not want to say that this constitutes "thermalization of the BULK
rotational kinetic energy (BRKE) of an isolated system" for two
reasons:

1. By my definition the system (i.e., the two wheels and whatever
mechanism was used to support them) didn't have any BRKE to begin
with.  I'm willing to stipulate that the system had RKE
(rotational kinetic energy), just not BRKE.  I'm also willing to
stipulate that the BRKE of *either* wheel was thermalized, but
then we are no longer talking about isolated systems.

2. Bulk rotation represents three modes of energy storage.  Thus,
if it *were* thermalized we would find that, after some
appropriate relaxation time, its value would fluctuate about an
average of 3/2 kT.  These fluctuations would, of course, be
evidence of proscribed interactions with some external heat bath
and they would serve as a crude thermometer.

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