Re: centrifugal force (cont)

[Rick Tarara <rtarara@SAINTMARYS.EDU>]

One of the reasons I approach weight as the gravitational force, is that we
have no direct sensation of that force.  Our perception of weight is due to
forces in the opposite direction from the gravitational force (the floor or
the chair).  When we analyze the perception of forces in accelerating frames
(from the point of view of someone observing from outside the frame) we can
see that time after time we end up perceiving forces in exactly the opposite
direction from the real (Newtonian) force.  Once this is realized, then even
within an accelerating frame we can always question whether or not our
perception of a force is 'reversed' by looking for the agent of the force.
I can then deduce that  even though I feel pushed away from the center of a
rotation, if I can't identify an agent pushing me outward then, most likely,
I am perceiving the force backwards.  If I feel weightless in free-fall, I
can deduce from my acceleration (the ground coming closer ever faster)that
my perception is false since there must be a force accelerating me
downwards.  This is all from the Newtonian viewpoint and doesn't require the
'existence' of  'virtual' forces.  It seems to me that it is only when you
want to reify these _perceived_ forces in accelerating frames that you need
to name them.

Rick (stuck in the Newtonian framework)

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Richard W. Tarara
Professor of Physics
Saint Mary's College
Notre Dame, Indiana
rtarara@saintmarys.edu
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----- Original Message -----
From: "RAUBER, JOEL" <JOEL_RAUBER@SDSTATE.EDU>
To: <PHYS-L@lists.nau.edu>
Sent: Thursday, December 12, 2002 12:13 PM
Subject: Re: centrifugal force (cont)


> > There is otherwise no fundamental reason for singling out the
> > centrifugal/coriolis effects from among the infinite possibilities of
> > "observer-accelerated " effects.
>
> There may not be a fundamental reason, but there are some very practical
> reasons for singling out those effects.  For starters, we live in such
> reference frames.  We often travel in vehicles that constitute such
frames.
> Furthermore, to the extent that general motion of a rigid body can be
broken
> into to translation plus rotation than such effects really are
fundamental.
> Joel R.