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, -Jeff Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=19174