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Re: Kinetic Energy elephant re-examined by formerly-blind person



John Denker wrote:

c) There are innumerably many viewpoints between
these extremes. We might call these mesoscopic
viewpoints. Among these is the thermodynamic
viewpoint, as exemplified by a spinning flywheel:
normally when we calculate "the" KE of the flywheel
we don't include the KE of the ultramicroscopic
thermal agitation, but we do include the rotational
KE, which is nonzero even though the center of mass
isn't moving.

You lost me here. Isn't rotational KE a prime example of nonthermal
energy? So why would you want to include that in a "thermodynamic
viewpoint"? Surely flywheels are covered in mechanics not thermo
class. I'm probably simply missing your point.

In any case, I'm not sure it's the *size* of the flywheel that is the
key issue, although I agree that it is important by the time we get
down to molecular rotors. Perhaps Mallinckrodt might have a few words
to interject here....

None of the above is sufficient to salvage the
ghastly "thermodynamic" formula
delta E = W + Q

That formula is a Bad Idea and no amount of
tinkering with the definition of W will fix it.

I credit you with getting me to slightly loosen my attachment to this
standard version of the FLT.

However, isn't it just fine for reversible processes?

Or is your dislike of this formula based on the idea that real-world
processes are irreversible? But don't we often make idealizations in
intro physics? Carl
--
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/