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Re: R&M replies from R



On Tue, 30 Apr 1996, Rauber, Joel Phys wrote:

...
The measurements I'm referring to are the ones that you can predict from
Newton's laws; namely the postion, velocity and acceleration of objects;
this is all Newton's laws can tell when you solve them;
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
This is the nub of the disagreement -- you seem to restrict mechanics to
computing and predicting correctly KINEMATICAL quantities only (position,
velocity and acceleration). But from measurements of kinematical
quantities mechanics must predict also accurate values of the important
dynamical quantities: real work done, real energy changes, both losses
and gains (the sort of things the energy companies make us pay real money
for), real mass values, real momentum changes. By introducing fictitious
dynamical quantities, such as a centrifugal force inside a turning car,
you completely obfuscate the issue of computing real dynamical quantities,
such as real energy expended, and then if and when you decide you want to
compute such quantities, you are going to have to go back and remove the
fictions (i. e., get back to an inertial frame) to see what real dynamical
quantities you actually have.

Instead, simply get rid of the rather strange idea that every acceleration
relative to any arbitrarily accelerated reference frame must have a force
associated with it. This is not what Newton's second law says -- Newton's
second law only says accelerations correspond to forces in inertial
reference frames -- and then when you come to need to compute accurate
values of dynamical quantities, you will not have to sort out fiction from
fact.

In short, you can do kinematics O. K. by reducing mechanics to kinematics,
but you can't do dynamics that way.



I've asked Marlow to send me a copy of the relevent posts here, so I can
address the
question.

No computations of the correct dynamical quantity were ever produced -- so
there's nothing to send. The claim, however, was that you could compute
the mass of the Sun using a frame in which both Earth and Sun are at rest
using fictitious forces to balance the gravitational attraction. I'd
like to see how that is done, but no one has done it yet.

A. R. Marlow E-MAIL: marlow@beta.loyno.edu
Department of Physics PHONE: (504) 865 3647 (Office)
Loyola University 865 2245 (Home)
New Orleans, LA 70118 FAX: (504) 865 2453