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----- Original Message ----- From: "John M Clement" <email@example.com>
To: "Forum for Physics Educators" <firstname.lastname@example.org>
Sent: Thursday, September 28, 2006 4:48 PM
Subject: Re: [Phys-l] teaching energy
One of the important things that needs to be done is that students
need to have a good analogy to be able to make sense of energy. The
basic one which is used in Modeling is the spring or rubber band. So
going from this to make sense of where E_p is located is to say it is
in the connection which acts like a funny rubber band. The system
approach is also used, but the connecting rubber band is a good
analogy, and is a lot less nebulous. In the case of some forces you
can readily see a strengthening of the field which makes one
comfortable with locating the energy in the field. However in the
case of gravitational the "field" decreases with increasing energy.
Actually, the STRENGTH of the field decreases, and the strength of the field does not have to equate with its energy. Taking the Modeling model of energy one step further, and incorporating the model of fiwld lines, I would argue that energy within a field results in an alteration of the field geometry, and it is THERE that the energy "resides". Allowing the geometry to revert to its orignal condition would transfer that energy to some object. The analogy to the rubber band is a visual example: The band changes its geometry as you stretch it, and energy resides in that altered geometry. Allowing the band to return to its "natural" geometry releases the energy.
In either case putting the energy in the field makes a good
visualization of "where" it is located.
And this is the primary focus for energy in Modeling - WHERE is the energy, and what changes occur when there is an alteration in the amount of energy.
Forum for Physics Educators