X-Message-Number: 19174
Date: Thu, 30 May 2002 09:05:52 -0400
From: Jeffrey Soreff <>
Subject: re #19169

>The difference is that "foot" in "foot-pound of work" means the displacement 
>through which the force acts, while "foot" in "foot-pound of torque" means 
>the lever arm, not the same thing at all, even though the same word or symbol 
>is used.

Torque is also the work per radian of angular displacement.  Since radians
are dimensionless, torque winds up having the same units as work.  The choice
of which units should be considered dimensionless is not altogether fixed by
physics.  Consider quantities like energy per mole.  A mole is really a
count of how many molecules are present (divided by Avagadro's number).  The
particle count is really an integer, a dimensionless number.  For ordinary
quantities of materials, however, the particle count is so large that only
the linear dependence of most quantities on the particle count matter, so
we can talk sensibly about "energy per mole" even if the real dependence of
the energy on particle count had, for instance, a form like
E(particle count) = k0 + k1*sqrt(particle count) + k2*particle count.

                                 Best wishes,

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