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



Jim wrote:

I was a little disappointed by the remarks in response to this post. They
seemed to say something like -- These are new thoughts, I have never heard
them before, I never learned anything like this in college..... I suppose
that Galileo received the a similar response -- no he was thought to be
evil, wicked, bad, and nasty. Swartz is spoken of here as "silly."

I must have missed those posts. Who said this stuff was new? Who made
ad hominem remarks?

Well maybe he doesn't understand work/energy, but most of the list use the
same language.

Did you come here to praise him or to bury him? I'm confused.

"energy
can _go_ to and from springs, gravitational fields, electric fields
..." And in the process reifies the imaginary concept of "fields."

Wouldn't you agree that if I drop a stone the energy of motion is
sourced by the gravitational field?

So his
first problem is that he doesn't understand the work/energy theorem.

I'm not sure about that. Partly yes. But partly I think he just
doesn't like the theorem and so sees problems with it that are really
straw men.

Then he attacks friction. Let's take a side bar: consider a cold widget
which is sliding on ice, the widget slows. therefore its level of energy
is decreased. The _only_ way to change the level of energy of a system is
to do work on the system. What then does this work? Obviously it is the
ice. But how? By exerting a frictional force. Hence, friction does
work.

You first say the ice does the work, then you say friction does the
work. Which is it? This is the same "dilemma" (too strong a word, but
it makes a point) that Swartz is wrestling with. Furthermore, if you
turn your attention to the issue of energy rather than force, things
look quite different. If you say the ice does work, then how is it
that it warms up? Carl
--
Carl E. Mungan, Asst. Prof. of Physics 410-293-6680 (O) -3729 (F)
U.S. Naval Academy, Stop 9C, Annapolis, MD 21402-5040
mailto:mungan@usna.edu http://usna.edu/Users/physics/mungan/