Re: Swartz letter in AJP (work-energy theorem)

[Jim Green <JMGreen@SISNA.COM>]

At 08:02 03 09 2004 , the following was  received:
> I'll be going away this weekend,

Carl is rightly fleeing the hurricane perhaps?

> so by the time I read the digests on
> Tuesday, this thread may have gone to rest. So permit me the liberty
> of responding to Jim as well. He says things very simply and plainly,
> so it's easy to understand and respond to him. God bless you for
> that, Jim! At the same time, it does make it easier to prod and poke
> at your statements. I hope you won't take it personally.

Carl, you are welcome to prod and poke all you wish. I am a very forgiving
person.  It is the lack of understanding of physics in someone that I
wrench over.

> >My point was that most of the list uses the same physics language as did
> >Swartz, so why were some on the list belittling him.
>
> Oh dear. Terminology is of course an issue. But I think if we're
> going to communicate, we need to tolerate some differences of opinion
> on the best way to define and use words.

Yes, Carl, but one of the usually overlooked problems is that language is a
product of understanding.

In the present case perhaps we should remember the case of  Aristotle
who  thought of the universe as being composed of something like earth,
water, air, and fire.  That "fire" was reified for centuries and we still
commonly do it.  And in the process teach poor physics.  Heat is not a
substance -- It does not flow -- Heat, Q, is work that is done to a
system.  When we use code-like language to give ourselves and our students
a poor understanding of thermo, we do no service to ourselves or our charges.

Then came Young who gave us the  concept of "energy."  Again he, and then
we, reified the concept to our disadvantage.  If we use the code-like
language, we fool ourselves and our charges into faulty physics
understanding.  Energy does not "exist" -- It is not a substance -- It does
not flow -- It is not transferred.  It can be considered a _property_ of
the system just as a color might.  However, its degree/intensity/level can
be changed by doing work on a system.  We don't reify the concept of work
-- We never say work flows.  It would be like like saying that blue exists
or flows or is transferred separately form the paint on the system.  I
agree this is not a perfect analogy but analogies are rarely perfect.

I suggest the carefully constructed language matters!

> >If the widget slows it loses energy,
>
> I'm very unhappy with this; it's too brief.

Yes, Carl, it is too brief as you read it, but remember that in the
original post I said "cold widget" with the hope that the ensuing
complication would be avoided.  But I must have forgotten what list I was
posting to and I hoped in vain.

> >I consider the issue of whether it is the force or the ice which does the
> >work somewhat spurious.

And still do.

Jim


Jim Green
mailto:JMGreen@sisna.com
http://users.sisna.com/jmgreen