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Re: ENERGY WITH Q



Likewise a distinction between the "sub-microscopic" and
"macroscopic" energies is useful but not essential. The
term "internal energy" was often debated on this list. I do
not remember who said what but the opinion I formed was
that the internal energy can be both macroscopic and sub-
microscopic. To illustrate this I would refer to a mechanism
with spinning wheels (at a non-zero T). Is this acceptable?

Sounds fine to me. I agree that what one means by "internal energy"
is context dependent. If you look at your whole system as one black
box, then everything but MV^2/2 (where M is the mass of whole system
and V is its CM velocity) is internal. If you view your system as a
bunch of blocks, pulleys, springs, earth, etc. then it helps greatly
to also split off the bulk translational, rotational, and potential
energies of each part. Finally if you look through a microscope,
there may not be any internal energy at all. I've called this level
1,2,3 analysis. I would do level 1-2 in mechanics and level 3 in
thermo *and not try to teach both at once!!!* I really don't like the
modern fashion in textbooks to introduce long lists of kinds of
energy in the mechanics part of the text. Save that for a chapter of
its own later. For now, let's get the kids to solidly understand work
and mechanical energy.
--
Carl E. Mungan, Asst. Prof. of Physics 410-293-6680 (O) -3729 (F)
U.S. Naval Academy, Stop 9C, Annapolis, MD 21402-5026
mungan@usna.edu http://physics.usna.edu/physics/faculty/mungan/