Ed Schweber (edschweb@ix.netcom.com)
Physics Teacher at The Solomon Schechter Day School, West Orange, NJ
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Hi
Brian McInnes responded to my question about a possible relativistic
violation of the Second Law of Thermo as follows:
Transfer of energy between two systems can
occur
(1) because of a difference in temperature between
the systems (ands non-adiabatic walls between
them) : heat
OR
(2) because of forces acting on the boundaries of
the systems: work. A transfer of energy through work
between objects at the same temperature is not a
violation of the second law.
Let me try to make myself clearer. In Joule's classic experiment the
paddles did work on the water because of their macroscopic motion through
the water. Had the paddles also been at a higher temperature, there would
also have been heat flow due to the transfer of vibratory molecular KE that
is not part of the overall macroscopic motion.
Now in the case I postulate here, the solid object will indeed also
inevitably be doing work on the fluid through which it moves. My point is
that due to the motion of the solid, its molecules now have a different
vibratory KE with respect to the frame of the fluid (although the still and
fluid still have the same temp - because temperature is correlated to
internal KE only in the center of mass frame of the object) and that during
collisions between these molecules at the surface of the box and molecules
of the fluid, there will also be an energy transfer which I am interpreting
as a heat flow.