Re: ENERGY WITH Q Here's my VOTE

[John Mallinckrodt <ajmallinckro@CSUPOMONA.EDU>]

On Wed, 14 Nov 2001, RAUBER, JOEL wrote:

> > Internal energy is all the energy of the system not dependent
> > on the motion or the position of the center of mass.
>
> Where in your accounting do you place the kinetic energy
> associated with the bulk motion of a rotating extended rigid
> body?

I tend to agree with Nick and I think his definition is completely
unambiguous in this regard (even though I see now that even HE
apparently doesn't agree with himself OR think that his definition
is unambiguous!)  I *generally* like to put rotational energy in
the "internal" category for the same reason that I like to put
bulk vibrations (as, for instance, in a "several masses connnected
by springs" system) in the "internal category."  Here's my
rationale:

It is true that "bulk" vibration modes can easily be populated
with FAR more than their fair share (a la the equipartition
principle) of the system energy and, therefore, probably should
not be considered when talking about the type of energy some like
to call "thermal energy", however, it is not obvious how to draw
the line between "bulk" vibrations and "thermal" or "microscopic"
vibrations so I'd just as soon include *all* vibrations as
contributors to "internal" energy.  If I do that, I feel
inclined to do the same thing with rotational energy which seems
to be on the same "kind" of energy as bulk vibration.

Having said all that, please note that I said "generally."  I am
perfectly willing to adopt a different stance in the face of a
specific problem for which it seems reasonable to do so.

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