Re: F=ma

[Joel Rauber <Joel_Rauber@SDSTATE.EDU>]

Mark Shapiro, better known as the IrascibleProfessor, wrote in part:
> Joel,
>
>         Is this really correct?  I know that some "force"
> measuring devices
> measure accelerations, but don't strain gauge type devices
> also measure
> "forces".

This had a long debate, without unequivocal resolution on the list. I don't
want to spend time on this again at this point (perhaps later); but I'd ask
how was the straing gauge of the types you are envisioning calibrated, and
were they calibrated by setting up equilibrium conditions, which are usually
determined by arranging things so that acceleration = 0; measuring it to be
zero I'd maintain.

>         Nevertheless, I do agree with those who view F=ma or (more
> correctly) F=d(mv)/dt as a prescription for measuring or calculating
> forces.

That's my metaphysics for looking at the 2nd law as well.  And actually
forms the basis for my above comments.

Joel