Re: [Phys-L] ?conservation of _internal_ energy

[John Denker <jsd@av8n.com>]

On 01/14/2016 12:26 PM, Herbert Schulz wrote:

> Why certainly work is being done by the `blue' box on the `red' box
> and the `red' box on the `blue' box via the interactive forces (which
> must be equal and opposite in direction of course).

You keep saying that, without proof ... indeed without evidence.

Here's my evidence.  

 1) The only "interactive force" is the contact force at the 
  point of contact.  By symmetry, there is no displacement at
  this point.  By definition, work is F·dx.  Here dx is zero.
  Therefore no work.  For details see
     https://www.av8n.com/physics/thermo/state-func.html#sec-internal-energy

 2) You could equally well replace the red system by a rigid
  infinitely-massive wall.  Again the displacement of the point
  of contact is zero and therefore the work is zero.

  As another way of obtaining the same result, the energy 
  transferred to the wall is p^2/(2M) where M goes to infinity,
  so the mechanical energy transfer (aka work) is zero.

  Are you claiming you can do work against the proverbial
  brick wall?  Really?

If you think my analysis is wrong, please explain where it
goes wrong and/or provide a comparably-specific argument that
produces a different answer.