🚀 go-pugleaf

   I just can't resist commenting again that pan balances-single or
double pan-operate by comparing gravitational torques on masses, even
though they may be calibrated in units of mass.  Pan balances would not
work at all if there were no gravity, and they wouldn't work properly
in a severely nonuniform gravitational field.  An inertial balance,
in which the mass to be measured is clamped to a platform supported
by springs that can be displaced sideways and set into vibration, will
work properly even in the total absence of gravity, so it does
determine mass.
   I think it is important, however to keep stressing to students the
distinction between mass and weight.  I think this may be a losing
battle, however.  I remember being told several years ago that the
National Bureau of Standards had finally given up on trying to get
manufacturers to stop giving weights in grams and kilograms, and the
"pound" is routinely used as a unit of mass in technical fields that
still employ the British system.  (That causes the constant appearance
of a mysterious factor of 32.2 in many formulas, which nobody seems
to understand...)
   I'd like to thank Harold Lefcourt for noting the use of the spring-
mounted chair for measuring mass while "weightless" in the AAPT video.
I'm going to see if my chairman will let me order that tape.

Steve Luzader
sluzader@fre.fsu.umd.edu