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Re: [Phys-l] teaching energy

"Actually students really have to go through some models in sequence, and some discarded models serve as bridges to the next level of understanding."

In the middle of the century an attempt was made to skip earlier / intro Physics. It failed and we, last I heard, have returned to what Baez named the "spiral" method.

bc, missed it.

John M Clement wrote:

I do not agree with everything that was written in the posted paper, but I do see the utility of treating energy as if it were something you can transfer. If a fluid analogy is used, that is OK at the beginning. Actually students really have to go through some models in sequence, and some discarded models serve as bridges to the next level of understanding.

The field concept is an important model that gives the student a handle on energy. After all it does away with spooky action at a distance. More modern undestanding of energy can come after they can handle a model where the potential energy resides in the field or in the connection between the objects. After all there is a connection between the objects or there would not be any forces.

The paper in question needs to make it clear that pedagogy is the focus. Indeed the philosopy behind modeling really takes the word right and wrong out of physics discussions, but focuses on getting student to build conherent models that successfully predict physical phenomena. And I believe I said that to my knowledge there have been no evaluations of the utility of using this philosophy.

John M. Clement
Houston, TX

| I certainly can not defend one point of view over the other | as being more correct. But I think that they are trying to | get students to build a consistent model of energy, so one | point of view may be more productive than the other.
Granted, but the document referenced, is actually saying that the other
viewpoint is *wrong*, implying incorrect physics?

Later they claim:

"If we claim that energy is stored in the gravitational field, and if a
change in energy content is
indicated by some change in the thing that stores it, then what changes
in the field when it gains
or loses energy?

R. McDermott wrote in part:
| The central theme is that the energy must reside somewhere. | Taken in that | context, the only "place" for it to be is in the field itself.
I don't understand the *must*; why not say it resides in the
configuration of the system. The change in the thing is . . . The
"thing" would be the two body system, the change in the thing would be
its configuration. For point-like objects that would be its separation
distance. Much like a mass-spring system.

They appear to me to be coming dangerously close to re-enforcing a fluid
& container model of energy; i.e. reifying the idea to a possibly
dangerous degree. Though I must admit to only a cursory glance at the
So while I found the document to be interesting and of value (I've
actually bothered to print it off) I worry about the reliance on the
field concept at this level. Both on grounds of practicality and
principle. In terms of principle, didn't Feynman and Wheeler write a
paper in the 40's showing that you could dispense with the field concept
in Electromagnetism. In terms of practicality, the field concept is
more abstract than the configuration of a system . . ., hence my worry.

Just some rambling thoughts for discussion.

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