Re: Displacement and position (was: displacement and graphs)

["RAUBER, JOEL" <JOEL_RAUBER@SDSTATE.EDU>]

one quibble:

> > Sure (I'm not sure of the "fixed" part), but that is not how I interpret
> > John's definition, see below.

> There is a difference between "fixed" and "initial".

Obviously, which is why I said "I'm not sure about the "fixed" part", which
was a reply to a different author.

And on to the substance (or lack thereof):

> I never required the reference to be the origin.  I never
> said that.  I
> never even imagined that.

With that understanding most of what I said is moot.  I inferred something
you did not mean to imply.

> I won't debate the alleged ugliness of something I never said.

No, you said it, or at least implied it as you admit below.  I.e. a
succession of reference points; and I'm alleging its ugliness, something you
have done in many other threads in reply to other authors.

> > Notice, that this
> > requires you to change your arbitrary reference for each
> succeeding interval
> > of motion of your object that you wish to consider.  Sure
> you can do that in
> > a consistant fashion, but UGH.

> De gustibus non disputandum.

Agreed and that ends up being what this strand has boiled down to!

> A glance at the literature will
> confirm that
> using a succession of references is utterly standard procedure:
>   -- for sound propagation in crystals in fluids,
>   -- for considering incremental displacement,
>   -- et cetera.

I glance at the literature and obtain a confirmation of what I'm saying,
define displacment over an interval without use of a reference point.

More precisely, I should say without interpreting the initial location as a
reference point, thus putting initial location and final location on an
equal footing.  But I suspect that we have reduced our differences to
semantics and aesthetic judgement.

Practically speaking, one defines an arbitrary reference point, the
coordinate origin, ( a different use of the words "arbitrary reference
point" that I mis-applied to JD's post) and proceeds by calculating
displacements as differences of position vectors.  We notice that this
procedure does *not* require a succession of reference points, which is to
say we keep the coordinate origin fixed!  A beautiful thing, I may add.  :-)