Re: Why work before energy in texts

[Tom Wayburn <twayburn@WT.NET>]

----- Original Message -----
From: Ludwik Kowalski <kowalskiL@MAIL.MONTCLAIR.EDU>
To: <PHYS-L@lists.nau.edu>
Sent: Tuesday, October 16, 2001 10:36 PM
Subject: Re: Why work before energy in texts


> Joe Heafner wrote:
>
> > > Regarding the chosen reference level, relativistically all potential
> > > energy must go to zero when the interacting particles are infinitely
> > > far apart.
>
> Ludwik Kowalski commented:
>
> > I would say the same is true for "mutually interacting particles"
> > in classical physics. Right?
>
> Joe replied:
>
> > I'd probably buy that. The point is that the zero point
> > really isn't rigorously arbitrary.
>
> Most introductory textbooks teach that PEgrv = 0 can be
> chosen arbitrarily at any distance between a particle and
> the center of our planet. For example, at the sea level, at
> the floor level, at the top of a laboratory table, at the roof
> of that building, etc. A blunder or an apparent paradox?
> Ludwik Kowalski


Hi Ludwik et al,

First note:  Normally, physics equations are written to solve one particular
problem, so an arbitrary zero is no hassle.   Also true of Third Law, which
says only that in their lowest energy states all substances have the same
entropy -- not  necessarily zero.

Second note:  F=ma is not so useful as F=kma, where in one system k = 1/g
sub c.   G sub c does *not* have units of acceleration.   (kma does not mean
what James Joyce meant by it.)

Regards to all / T