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



John Denker wrote:

See if this revised version is any better:

There are innumerably many gray areas between these
extremes. We might call these mesoscopic viewpoints.
Among these is the view that divorces mechanics from
thermodynamics, as exemplified by a spinning flywheel:
in mechanics class, if somebody asks you to calculate
``the" KE of the flywheel you probably aren't expected
to include the KE of the ultramicroscopic thermal
agitation, just the rotational KE. For a flywheel,
-- The holoscopic KE is zero, because the center
of mass isn't moving;
-- The mesoscopic KE is the usual rotational KE;
and
-- The ultramicroscopic KE includes the above
plus the thermal agitation. In this viewpoint, the
thermal KE is the largest contribution unless the
flywheel is rotating pretty fast.

If somebody asks you to calculate the thermal KE, you
aren't expected to include the organized rotational KE.
So you would have to evaluate KE[microscopic] and
subtract off KE[mesoscopic].

Yes, I'm basically happy with this and certainly agree with the
spirit of it, my only slight remaining qualm being the size issue,
ie. I normally think of a "mesoscopic flywheel" as some kind of MEMS
device. 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/