Re: [Phys-l] teaching energy

[Carl Mungan <mungan@usna.edu>]

Jeff Schnick wrote:

> In the reference frame in which the center of mass of the system is at
> rest, both the kinetic energy and the potential energy of a system
> contribute to the inertia of that system (where the potential energy
> contribution may be negative).  The rest masses of the particles in the
> system represents yet another contribution to the total inertia of the
> system.  Multiplying the total inertia of the system by the square of
> the speed of light gives the total energy of the system.  Thus, we have
> three broad categories of energy: kinetic energy, potential (a.k.a.
> configuration) energy, and rest mass energy.

This suggests identifying rest mass energy with internal energy. But 
that isn't really a clean third category, insofar as it includes all 
of the hidden kinetic and potential energies of the system. In turn, 
what is "hidden" depends on how closely you are willing to look, ie. 
macroscopically (the whole system is one object), mesoscopically (the 
system consists of a set of blocks, springs, flywheels, planet, 
etc.), or microscopically (molecules translating and rotating, atoms 
vibrating, and maybe even electrons orbiting). Carl
--
Carl E Mungan, Assoc Prof of Physics  410-293-6680 (O) -3729 (F)
Naval Academy Stop 9c, 572C Holloway Rd, Annapolis MD 21402-5002
mailto:mungan@usna.edu     http://usna.edu/Users/physics/mungan/