Re: Internal or external?

[Ludwik Kowalski <KowalskiL@MAIL.MONTCLAIR.EDU>]

That is easy to fix. On the other hand, what harm can result
from using the common shortcut, "force acting on a mass"?

And, for the sake of argument, forces (and potentials) are
properties of interactions. Should we also insist on the "earth
acting on the rock with the force W"? Would the "F acting
on Q" irritate you? Would you object to the "effect of that
potential on the trajectory of Q"?

In my opinion harmless shortcuts are useful. This, however,
does not apply to situations in which weight and mass are
used interchangeably by students. "Weight acting on a mass"
can be useful to emphasize the difference between m and W.
Ludwik Kowalski

Brian McInnes wrote:

> Here follows a "minor" point that I find irritating.
>
> In the recent thread on treatment of Atwood type situations phrases
> such as "each mass is acted upon by two forces" occurred from time to
> time.  I think that we shouldn't confuse the property "mass" with the
> name of the object.  I'd call it "object" or "body" or (better)
> "block" but not "mass" or even "weight".