Re: Newton's 3rd law? was Re: inertial forces (definition)

[Bob Sciamanda <trebor@VELOCITY.NET>]

Hi Jack,
Out of curiosity, can you indicate any mathematical statements in Physics
where " = " does not mean a numerical (or perhaps vector or tensor)
equality?

Bob

Bob Sciamanda (W3NLV)
Physics, Edinboro Univ of PA (em)
trebor@velocity.net
http://www.velocity.net/~trebor

----- Original Message -----
From: JACK L. URETSKY (C)1998; HEP DIVISION, ARGONNE NATIONAL LAB ARGONNE,
IL 60439 <JLU@HEP.ANL.GOV>
To: <PHYS-L@lists.nau.edu>
Sent: Sunday, October 24, 1999 1:29 PM
Subject: Re: Newton's 3rd law? was Re: inertial forces (definition)


> Hi Bob-
>         I think we are getting close to communicating when you write:
> > *************************************************
> > The centripetal component of the acceleration is v^2/r .
> > The centripetal component of the net force is mv^2/r .
> > ***************************
> >         Au contraire.  The quantity mv^2/r is the mass times the
> acceleration
> > which is numerically equal to the applied force (contact or one of the
> forces
> > that act at a distance).
> > . . .
> >                                 Regards,
> >                                         Jack
>
> It depends on what the meaning of "is" is!
> In my above statement "is" symbolizes a numerical equality.
> *************************
>         My point was: it depends upon the meaning of "equals".
> "Equals" can mean either identity (mathematically, "of the same class
as")
> or numerical equality of non-identical quantities.  Your little
political
> joke puts a strained meaning on "is" which, as a form of "be" indicates
> identity - but then perhaps that is what you are recognizing.
>         The confusion of the two meanings of "equals" is very common
among
> students, which is why I belabor the point.
>                                 Regards,
>                                         Jack
>
>         "I scored the next great triumph for science myself,
> to wit, how the milk gets into the cow.  Both of us
> had marveled over that mystery a long time.  We had
> followed the cows around for years - that is, in the
> daytime - but had never caught them drinking fluid of
> that color."
>                 Mark Twain, Extract from Eve's
>                 Autobiography