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Re: operational F, m, and a (velocity measurements with fish-scal es)



At 05:09 PM 10/19/01 -0500, RAUBER, JOEL wrote:
one cannot use the spring to measure other forces, ***without other
kinematical measurements***

1) I am mystified by the reference to "other" forces.
What other forces? Other than what?

The spring-scale is advertised to measure the force applied to its
hook. Nothing more, nothing less. (There will of course be imperfections
and nonidealities, but that doesn't change the concept.)

I will agree that a spring-scale here on my desk doesn't measure the force
between Alpha Centauri and Beta Centauri, or any "other" force, other than
the force applied to its hook. But that really ought to go without
saying. What is the point of discussing this?

2) I am totally mystified by the emphasized words, "without other
kinematical measurements" (henceforth WOKM).

I have given an example (scale + scale + chassis) wherein a scale measures
a force WOKM. The reading on the scale tells you the force WOKM.

Perhaps WOKM is some general philosophical statement. If the point is that
you cannot measure mass WOKM or length WOKM or time WOKM or temperature
WOKM or color WOKM, then by extension you cannot measure force WOKM -- but
this doesn't tell us anything interesting about force _per se_. So once
again I'm wondering what is the point of discussing this?

=============

I have described a fully-realizable physics experiment that illustrates
what I mean (scale + scale + chassis). The counterarguments have uniformly
lacked any experimental or theoretical _physics_ rationale. Unless
somebody adduces a _physics_ reason to believe otherwise, I will continue
to believe my spring-scale can measure a force WOKM, and I will have
nothing more to say. I am not interested in a non-physics-based contest to
see who can argue the loudest or the longest; I hereby concede that contest.