Re: Physics Definition of Work -- Quis custodiet ipsos custodes?

[Jim Green <JMGreen@SISNA.COM>]

> On the other hand we do have a standard definition of "work
> done by a force' or "work done by the net force". It a dot
> product of F and dX; I am never confused about the sign.

Precisely, Ludwik, so use this!!

> I am aware of the dilemma "Work done on a piston (by a gas) or
> work done by the piston (on the gas)? If one is positive then
> the other must be negative. But which one?" I WOULD SUPPORT
> ANY CONVENTION DESIGNED TO ELIMINATE PRESENTLY EXISTING AMBIGUITY.
> Who should we ask for changes of conventions (for the sake of
> pedagogical and practical convenience)?
> Ludwik Kowalski

Conventions are the crutch of pedantry.  Just do the physics -- and teach
the kids in the process.

Consider the ubiquitous enclosed cylinder with a piston:  If a force
presses the piston inward W=Fdotdx>0 ON the cylinder and deltaE>0  If the
gas in the cylinder presses the piston outward the W=Fdotdx >0 ON the
environment therefore W<0 on the cylinder=system and deltaE<0.

Why do we worry about the stumbling blocks.

Jim Green
mailto:JMGreen@sisna.com
http://users.sisna.com/jmgreen