On Mon, 12 Nov 2001, Joseph B. Reid wrote: > ... > How can one denote the distinction between a newton metre as the unit to > measure energy and the newton metre as the unit to measure torque?
The quantity symbols denote vectors, not the unit symbols. > How, in Gene's notation, does one distinguish between N.m as a scalar > and N.m as a vector? Again, the quantity symbols (e.g. boldface italic fonts) denote vector quantities, not the unit symbols. For the examples of work and torque, one might adopt the habit of consistently writing J (joule) for work and m.N for torque, but this is not an established convention. Note, that I wrote m.N, the unit symbols in the same order as follow from torque T = r x F (not N.m which corresponds to F x r = - T. > How would Gene distinguish between the unit for measuring > radiant power from the unit for radiant intensity, or how does he > distinguish the difference between the units for liminous flux and > luminous intensity? I quote from NIST SP 330 (2001 Edition), Page 3: It is important to emphasize that each physical quantity has only one SI unit, ... The inverse, however, is not true; in some cases the same SI unit can be used to express the values of several different quantities (see p. 12)." The examples cited on Page 12 are heat capacity and entropy (J/K); and electric current and magnetomotive force (A). In other words, a quantity name (or symbol) implies a unit name with no ambiguity, but a unit name (or symbol) alone, does not always reveal the quantity in question. Only context can do that. Gene.
