Re: Thermal Energy

[Hugh Haskell <hhaskell@MINDSPRING.COM>]

At 23:20 -0700 3/4/02, Jim Green wrote:
> At 20:12 04 03 2002 , you wrote:
> > I would say that the statement is true. The thermal energy as described is
> > internal and does not change because of the motion of the object. A balloon
> > does not get larger when it is traveling down a highway at the speed limit.
> > Why do you ask?
>
> Umm. I don't think so , Cliff. Tim says that he defines "thermal energy" as
>   "the total energy of the particles in a material -
> both kinetic energy (vibrations and movement within and
> between particles) and potential energy (determined by
> forces that act within and between particles "
>
> But, if the golf ball is being translated at some finite velocity through
> the air, the "total energy of the particles in the material"  -- according
> to _his_ definition -- would incorporate the translational kinetic energy
> of the particles.  Thus the level of the property of his thermal energy of
> the golf ball would be higher in flight.   The internal energy of the golf
> ball would not.
Maybe that's what Tim said, but I have never seen a definition of
"thermal energy" that would agree with that. I'm not even too sure
about the potential energies among the atoms of the object (usually
negative). My understanding of "thermal energy" has always been the
random kinetic energy of the atoms in an object (or collection of
objects, like a gas or a liquid), measured relative to the center of
mass of the system. That would exclude an organized rotational motion
of the system as well as translational kinetic energy of the center
of mass. In other words, "thermal energy," pretty much corresponds to
the kT energy associated with the system.

Hugh
--

Hugh Haskell
<mailto://haskell@ncssm.edu>
<mailto://hhaskell@mindspring.com>

(919) 467-7610

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