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

[Jim Green <JMGreen@SISNA.COM>]

> If the widget only, then there is an energy transfer
> which we attribute to the work done by the force
> between the ice and the surface of the widget.

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.

The problem with the language is that the energy is _never_
transferred!  The level energy, a property of a system,  may be changed by
doing work, but energy never moves --- unless of course the system
moves.  It is not a fluid which flows.  It is in fact not anything.  When
we reify energy, we do our students a major disservice.

And Larry is precisely correct.  If the widget slows it loses energy,
therefore work _must_ have been done on the widget.  The ice does the
work.  We call the attendant force friction.  There is a loss of energy
hence the work done is negative.

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

Why is this such a major problem?

Jim


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