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

[Herbert Schulz <herbs@wideopenwest.com>]

> On Jan 14, 2016, at 1:14 PM, John Denker <jsd@av8n.com> wrote:
>
> In the context of:
>  https://www.av8n.com/physics/thermo/state-func.html#sec-internal-energy
>
> On 01/14/2016 08:23 AM, Herbert Schulz wrote:
> > Yes, imagine a gas instead of the spring. As the gas expands it
> > pushes the piston and does work. 
>
> I say it does /not/ do work.  No work is done by (or on) the blue
> system. There is no F·dx: At the place where there is a nonzero
> force, there is no displacement. At places where there is a
> nonzero displacement, there is no force.

Howdy,

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).

Good Luck,

Herb Schulz
(herbs at wideopenwest dot com)