Re: apparent weight--Pedagogy

["Rauber, Joel Phys" <RAUBERJ@mg.sdstate.edu>]

I agree with most of what Richard wrote below, but I like seeing peoples 
views from the various perspectives and levels of sophistication; although 
we do need to remember that often questions are intended to be of the type 
"how do I deal with this at the introductory level".

Of course, they aren't all at the level Pedagogy; for example, "does 
centrifugal force do work and if so, in what frame of reference?" are not 
pedagogical issues or questions.

Joel
 ----------
From: Richard W. Tarara
To: QuistO; RAUBERJ; phys-l
Subject: Re: apparent weight--Pedagogy
Date: Thursday, February 19, 1998 11:22AM

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.  Some on the list obviously prefer the former and find certain
advantages (not the least of which is philosophical) in doing so while
others (like myself) see more problems created by that approach than solved.
For me, I have enough trouble understanding anything that Dave Bowman posts
myself, much less even imagining that I can help my introductory students to
that kind of understanding.  The weight of Physics Educational Research
shows that students have enough trouble with the Newtonian view, so can we
really try to jump them into an Einsteinian one {an area for more PER
perhaps}.

If one chooses to work in the Newtonian framework (as do most introductory
texts) then one _does_ have to deal with the sensations experienced in
accelerating frames.  These can still be dealt with in a Newtonian way (up
to a limit) and 'Apparent Weight' is one of those ways.  In this framework
and with rotating frames, a perceived _outward force_ is usually fictitious
{I also try to eschew the 'C'-forces in favor of 'C'-accelerations and the
forces that cause them}.

The debate here really then comes down to whether or not to limit
introductory instruction to trying to attain a Newtonian understanding or
whether to jump directly to today's understanding.  My own view has always
been that the Physics Curriculum (more so than other sciences) is a spiral
curriculum where we go over the same general content over and over but at
ever increasing mathematical sophistication AND from an ever advancing
historical perspective.  This is not to say that the 'jump to the present'
approach can't work, only that it hasn't been proven to work (any better)
than the more traditional approach.

Rick


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