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

[Robert Cohen <Robert.Cohen@PO-BOX.ESU.EDU>]

On Saturday, October 20, 2001 5:24 AM, John S. Denker wrote:

> 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.)

John,

Let's examine the object that is applying the force to the spring's hook.
There may be other forces acting on the object besides that applied by
the spring.

1. Is it possible to determine the magnitude of the other forces
on the object only knowing the force as measured by the spring?

Apparently, this is not the question you are interested in.  However, I
think
you will agree that it is not possible without using F=ma and, consequently,
other kinematical measurements (to get a).

A separate question is "what is the point of question #1?"

I think the answer has to do with determining forces such as Fg, Fe, etc.,
but perhaps Joel can help us out here.

--------------------------------------------
Robert Cohen           rcohen@po-box.esu.edu
570-422-3428         http://www.esu.edu/~bbq
Department of Physics
East Stroudsburg University
East Stroudsburg, PA  18301
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