Re: POE summary (was Re: Work/Energy theorem?)

["Rauber, Joel Phys" <RAUBERJ@mg.sdstate.edu>]

>    I'd like to get back to the original question for a moment.  As I
> understand it you have an observer on a moving train who is looking at
> tree someplace on the ground.  The observer on the train calculates the
> K.E. of the tree.  The train is then decelerates to a stop, and the
> observer calculates the K.E. of the tree again and finds that it is zero.
> Someone then wanted to know where the lost K.E. went.

>    My naively classical mind said that it didn't go anywhere - that
> the observer on the train decelerated so the change in KE was not measured
> in an "inertial" frame so it was a physically meaningless number.

When the person on the train makes his/her measurements, they were doing so 
in inertial frames of reference; BUT they weren't different frames of 
reference.  This no more mysterious then noting that the two frames of 
reference (the original constant velocity train frame and the frame of the 
person handcuffed to the tree) measure the kinetic energy to be different. 
 Kinetic energy is not a Galilean Frame invariant concept (to use fancy 
language).

Joel

Disclaimers,
This is a quick off the cuff response, as are most of my comments.