Re: [Phys-L] foundations of physics: Galilean relativity, including KE

[John Denker <jsd@av8n.com>]

On 09/30/2015 03:10 PM, Jeffrey Schnick wrote:

> Thanks for going with the intended meaning.

:-)

> My thinking is that for any system A, in any inertial reference
> frame, there is a system B having a three-momentum that is the
> negative of that of system A.  So, for system C, consisting of both A
> and B, in that inertial reference frame, the total energy of system C
> is the mass of system C and it is the internal energy of system A +
> the internal energy of system B + the kinetic energy associated with
> the motion of the center of mass of system A + the kinetic energy
> associated with the motion of the center of mass of system B + the
> potential energy associated with any interactions that might be
> taking place between systems A and B.  In other words all the energy
> of system A contributes to the mass of system C,

So far so good ...

> hence, all the energy of system A is mass. 

Does not follow!

Here's an industrial-strength counterexample, where *none*
of the energy of system A is mass:
  http://www.av8n.com/physics/spacetime-welcome.htm#sec-invariance-conservation