RE: Supplementary S.I. units

[David Bowman <dbowman@tiger.georgetowncollege.edu>]

I personally don't have a very strong opinion about whether or not angles
should be considered to have their own (engineering) dimension.  I would
have a slight preference to keep angles dimensionless, since (being a
theorist) I think there are too many needless dimensions for physical
quantities as it is, and I would not want to make the situation worse. :)

Regarding where Donald wrote:
> ...
> I also note that to write 1 kilogram = 2.2 pounds is improper, because the
> equation is inhomogenous and is not coherent with respect to units and
> dimensions. We should avoid equating apples and oranges unless we are only
> interested in "the number of pieces of fruit". We should say, "A one
> kiolgram *mass* at the earth's surface *weighs* 2.2 pounds." Even that
> needs more precision of language.

To help confuse the issue let me point out that according to the NIST's
Special Publication 811 the avoirdupois pound is defined to be *exactly*
0.45359237 kg of *mass*.  A 1 pound force (lbf) is the weight of a
1 lb mass in a standard gravitational field.  *If* this standard field
strength is taken as the 'official' value of 9.80665 m/s^2 then a 1 lbf
corresponds to *exactly* 4.44482216152605 N of force.

David Bowman
dbowman@georgetowncollege.edu