Re: displacement and graphs

[Rick Tarara <rtarara@SAINTMARYS.EDU>]

If you never introduce displacement, then isn't there a problem with
instantaneous velocity?  That is, by the time you get to v = ds/dt   (I try
to get here even in the non-calc courses) you want the thing you are taking
the derivative of to be a vector.  The position is not a vector, only the
change in position, so v = dP/dt   (P = position) doesn't really work and v
= d(delta-P)/dt is a bit clumsy.  :-)

Rick

**********************************************
Richard W. Tarara
Professor of Physics
Saint Mary's College
Notre Dame, IN 46556
rtarara@saintmarys.edu

FREE PHYSICS INSTRUCTIONAL SOFTWARE
www.saintmarys.edu/~rtarara/
PC and MAC software
NEW! SIMLAB2001--AIRTRACKS & BALLISTIC LAUNCHER
CD-ROMs now available
******************************************************

----- Original Message -----
From: "Joseph Bellina" <jbellina@saintmarys.edu>
To: <PHYS-L@lists.nau.edu>
Sent: Wednesday, October 10, 2001 8:10 AM
Subject: Re: displacement and graphs


> This confusion has prompted me to avoid the term displacement...do it
> really serve a purpose that change in position would not.  We don't have
> a separate word for change in velocity...why do we need one for
> position.
> Could it be that this preferential treatment of position, that is
> creating a word for the change, is somehow connected with the naive
> preference for position rather than velocity when thinking about how
> objects move?  That just popped into me head so I'm not sure I would
> defend it strongly...but it is curious.
>
> joe