Re: Thermal Energy - thermalization of rotational energy

[Jim Green <JMGreen@SISNA.COM>]

John assures me that his question is sincere -- I would never suspect that
he really does not know what is usually included in "internal energy".  And
I would prefer to begin with his/the list's definition of "thermal energy"
as I posed in my last post.

But he says that he would include bulk rotational an translational motion
in "internal energy" so I guess that there is in fact a basis for a
discussion here.

Let me start with what might appear to be off topic:  An inertial reference
frame:  I asked this question in my junior mechanics class and poor Prof
Gardner was sorely stumped!  The answer of course is that it is a reference
frame in which Newton's Laws hold.

Now I realize that in some thermal physics classes the topic of
thermodynamics doesn't come up.  But surely we all know the First Law in
addition to a bit of stat.

Internal energy is the state variable where the first law is valid.  And I
suppose we should include the Second Law as well.  It includes all the
random motion KE (trans, vib, rot) and atomic PE -- usually with a bit of
hand waving.

Surely it does not include bulk rotational or translational motion.

But I am left with the notion that I have missed something.

Now someone please tell me what is meant by "thermal energy" and for what
the concept might be used.

At 15:54 07 03 2002 , you wrote:
> On Thu, 7 Mar 2002, Jim Green wrote:
>
> > I do understand what is usually meant by "internal energy" and how that
> > concept is used/useful,
>
> Jim,
>
> I'm interested (seriously) in hearing what you think is usually
> meant by "internal energy." In particular I'd be interested in
> knowing whether you would say that it includes bulk rotational
> kinetic energy and large amplitude macroscopic system vibrations.
>
> If so, would you consistently put those kinds of energy in the
> same category as atomic scale vibrations and rotations or would
> you sometimes put them in some third category?
>
> If not, would you consistently put them in the same category as
> bulk translational kinetic energy or, again, would you sometimes
> put them in some third category?
>
> John Mallinckrodt     mailto:ajm@csupomona.edu
> Cal Poly Pomona         http://www.csupomona.edu/~ajm