Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: apparent weight--Pedagogy



Where I think we really are in this discussion is at the level of Pedagogy.
Most of us will admit that the 'Bowman' level description of gravity is the
_most_ correct we have and that if we do analyses from within accelerating
frames then one must deal directly with forces that don't conform to
Newton's Laws. The question now however, is DO we try to jump our
Aristilean students directly into late 20th Century physics, or do we take
the intermediate step of trying to first bring them into the Newtonian
world

Rick, the only reason I mentioned the equivalence principle in
the first place in this discussion is that I was talking to
physicists, not students. I can use Einstein to justify my
position with members of this group (with the exception of those
with mystical commitments). There is absolutely no reason to
invoke Einstein or GR or anything slightly sophisticated when
presenting the topic to students. Weight is what is measured on
the scale, in the bathroom, on a level floor. It has a magnitude
mg. It points to local down. There are NO pedagogical problems!

Later on, when you feel they are ready to absorb the blow (or
never with many of them) you can let on the "g" contains a
contribution from the centrifugal force. If a student asks
whether that might indeed be the case you can tell him that,
indeed, it is the case. "g" is the local "acceleration of
gravity". It is what is measured by gravimeters. It varies from
place to place on Earth's surface due to varying latitude, ore
bodies, etc. It is approximately equal to the sum of a spherical
Earth Newtonian term and a centrifugal acceleration term, plus
all the shmutz that make gravity surveys worthwhile.

Why should physics teachers teach differently?

Leigh