Re: Centrifugal force

["Bob Sciamanda" <trebor@velocity.net>]

Bob Sciamanda   trebor@velocity.net
Dept of Physics
Edinboro Univ of PA  http://www.velocity.net/~trebor
Edinboro, PA   (814)838-7185
-----Original Message-----
From: Jerome Epstein <jerepst@worldnet.att.net>
To: phys-l@atlantis.uwf.edu <phys-l@atlantis.uwf.edu>
Date: Saturday, May 02, 1998 12:16 AM
Subject: Re: Centrifugal force


> Bob Sciamanda wrote:
> >
>
> > I think Newton believed in absolute time and space and, at the outset,
> > fully expected that the best that he might do would be to find a
physics
> > which would work only for an observer at absolute rest.  The existence
of
> > a whole class of inertial frames was an unexpected (and, I think,
> > undesired) conclusion, not an assumption.
>
> The invariance under the Galilean transformation (between inertial
> frames) was already implicit once it was clear that the fundamental laws
> involved acceleration and not velocity. Acceleration is invariant under
> the change to a uniformly moving frame. YOu are correct, however, that
> Newton clearly believed in sbsolute space and absolute motion ever after
> knowning that his mechanics was invariant under Galileian
> transformations.
> > He certainly believed in INVARIANT force pairs of interaction between
> > bodies as the basis of his mechanics.  Only the inertial observer can
use
> > observed acceleration as the measure of these forces, since
accelerations
> > are frame dependent, but Newtonian forces are frame invariant,
>
> I am baffled by this. Acceleration is unchanged by a transformation to a
> frame in uniform motion with respect to the first frame. For inertial
> frames, accleration is NOT frame dependent.

Be not baffled!
Note that my last statement includes All INERTIAL observers as valid
users of F=ma.
I thought that I was clearly implying that accelerations are not
invariant with respect to a GENERAL transformation.  The point is that in
Newton's view only inertial frames correctly measure absolute
accelerations, the measure of (invariant) forces.  To Newton, EVERYBODY
should "see" the same forces in nature;  but different observers will in
general measure different accelerations, only inertial observers will
measure absolute accelerations.  Hope this un-baffles :)