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

["JACK L. URETSKY (C)1998; HEP DIVISION, ARGONNE NATIONAL LAB ARGONNE, IL 60439" <JLU@HEP.ANL.GOV>]

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