Ed Schweber (edschweb@ix.netcom.com)
Physics Teacher at The Solomon Schechter Day School, West Orange, NJ
To obtain free resources for creative physics teachers visit: http://www.physicsweb.com
Hi again,
Let me just push this a bit further. Herb Schulz, David Bowman, and Jack
Uretsky all point out that internal energy is measured in the rest frame of
the object.
Imagine that there is a solid object at rest and in thermal equilibrium
with a surrounding fluid. They are both at the same temperature. Now a force
accelerates the solid object without without adding to its internal energy.
Is this in some way unreasonable. If not, the solid object should have
the same temperature as before and the same temperature as the fluid through
which it is now moving. But from the rest frame of the fluid would not the
solid object now have a different average kinetic energy per molecule?
Would there not now be a transfer of this molecular KE between the solid
and the fluid -that is a transfer of heat between objects at the same
temperature - in violation of the Second Law of Thermo?