Re: Why work before energy in texts

[Bob Sciamanda <trebor@VELOCITY.NET>]

When you correctly use a work-energy theorem (validly derived from Newton's
laws) to calculate a numerical quantity you are on the solid ground of a
mathematical model - a testable numerical equality.

When you interpret these numerical results in terms of "particular energy
losses, gains, transfers, transformations, etc  among particular objects",
you are in the completely different realm of a conceptual model - a shaky
ground of subjective taste based on metaphorical associations with everyday
real and imagined human experience.

You can do your students no greater service than to emphasize this
distinction when you explain "How you know".

Bob Sciamanda (W3NLV)
Physics, Edinboro Univ of PA (em)
trebor@velocity.net
www.velocity.net/~trebor
----- Original Message -----
From: "Larry Cartwright" <exit60@CABLESPEED.COM>
To: <PHYS-L@lists.nau.edu>
Sent: Sunday, October 14, 2001 11:31 PM
Subject: Re: Why work before energy in texts


> Jim Green wrote:
> > I am not sure why you seem to denigrate the noble quality of "equal"
with
> > "merely".
>
> Just a personal perspective.  It seems rarely do we identify two things
> that initially appear to be different but turn out to be identical, and
> I view such identity as far more profound than the uncountable physical
> examples of things that are just mathematically equal.  To me it is the
> difference between things that are equal because *nature* has made them
> immutably so, and things that are equal because *we* have chosen to make
> them so.
>
>
>
> Best wishes,
>
> Larry
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Larry Cartwright   <exit60@cablespeed.com>
> Retired (June 2001) Physics Teacher
> Charlotte MI 48813 USA
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> "Information is not knowledge,
>  knowledge is not wisdom,
>  and wisdom is not foresight.
>  Each grows out of the other
>  and we need them all."
>             (Arthur C. Clarke)