Re: Internal or external?

[Larry Smith <Larry.Smith@SNOW.EDU>]

> 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".

At 6:37 AM -0400 10/10/1999, Ludwik Kowalski wrote:
> That is easy to fix. On the other hand, what harm can result
> from using the common shortcut, "force acting on a mass"?

I quote from NIST's "Guide for the use of the International System of Units
(SI)," page 22:

----begin quote-------
To avoid confusion, when discussing quantities or reporting their values,
one should distinguish between a phenomenon, body, or substance, and an
attribute ascribed to it.  For example, one should recognize the difference
between a body and its mass, a surface and its area, a capacitor and its
capacitance, and a coil and its inductance.  This means that although it is
acceptable to say "an object of mass 1 kg was attached to a string to form
a pendulum," it is not acceptable to say "a mass of 1 kg was attached to a
string to form a pendulum."
-----end quote------

Cheers,
Larry


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