Re: Apparent Weight

["A. R. Marlow" <marlow@loyno.edu>]

On Mon, 23 Feb 1998, James W. Wheeler wrote:

> > From B.P. Cowan, "Classical Mechanics" Routledge and Keegan Paul plc 1984
>
> Mach's Formulation of Newton's Laws
>
> 1.  (Experimental Proposition) When two bodies interact they induce in
> each other oppositely directed accelerations.
>
> 2.  (Definition) The mass-ration of any two bodies is the negative inverse
> ratio of their mutually induced accelerations.
>
> 3.  (Experimental Proposition) The mass ratio of bodies is independent of
> their physical state.
>
> 4.  (Experimental Proposition) The accelerations which any number of
> bodies induce in a body are independent of each other, i.e. forces add as
> vectors.
>
> 5.  (Definition) Force is defined as the product of the mass of a body and
> its acceleration.
>
>
> Comment-(mine)  Forces are useful because they seem to obey repeatable laws.
> ...
 
Everything in the above quotation really seems to say *accelerations* obey
repeatable laws.  Force is defined as a seeming afterthought as mass times
accelerations, apparently without regard to any inertial reference frames.

Question 1:  Why bother to define a new notion (force) if it is always and
everywhere just a multiple of accelerations?  Usually, when physics
makes the discovery of such an identification of terms thought
previously to be distinct, in the name of economy of terms, one of the
terms is either eliminated or its usage reallocated.  
Question 2:  I don't have Mach's work handy.  Does he ever make use of
inertial reference frames?

If memory serves me, Einstein was very much enamored as a young man of
Mach's program.  They corresponded fairly frequently, but their views
diverged as Einstein gradually worked out general relativity with its
emphasis on the the privileged role of inertial frames.  Mach himself then
became very critical of general relativity, and his own program became
superseded in the minds of most physicists as a beautiful logical
structure which can't quite be reconciled with reality. Can anyone fill
us in more accurately on the history here, and the present status of
Mach's ideals?


A. R. Marlow                          E-MAIL:  marlow@loyno.edu
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