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Re: [Phys-l] Configurational energy



On 10/16/2007 11:21 PM, Dan Crowe wrote:

I often use "configurational energy" as a preferred synonym for
"potential energy". Using the phrase "configurational energy" helps
avoid two common misconceptions about potential energy, because it
doesn't imply that the quantity isn't really energy, and it implies that
the energy is due to an interaction between two or more objects.

I'm not sure what problem we are trying to solve, but in any case,
that approach probably isn't the right way to solve it.

1) Students have misconceptions. That comes with the territory.
We deal with it.

2) If students are basing their misconceptions on the _names_ of
things, then that's a problem unto itself, a major high-level
problem.

The rule is:

A name is not an explanation.

This is a rule of language, not restricted to physics.

Here's how I explain it: Chocolate turtles are not made from
turtles. Milk of magnesia is not made from milk. A titmouse
is not a mouse. As Voltaire pointed out, the Holy Roman Empire
was neither holy, nor Roman, nor an empire.

If anybody thinks that potential energy is not energy because
of the _name_, they have got a major problem, and changing the
name is just re-arranging deck chairs on the Titanic.

/Sometimes/ knowing the etymology is helpful, but (a) you'd
better have the correct etymology, and (b) even then it may
be only a mnemonic, or even less than that; see item (5)
below. A name is not an explanation.

This point (2) is very important. It transcends the topic of
energy, potential or otherwise. It needs to be taught separately.

3) As for whether this-or-that is "due to an interaction between
two or more objects":

We should teach that *all* of physics is invariant under a shift
in position. This is super-important. This "relativity of position"
is one of the oldest deep principles, even predating Galileo.

As a corollary, you can't have *anything* (energy or otherwise)
as a function of abstract position. Any physical observable
must involve some sort of interaction between "two or more"
somethings.

A sub-corollary applies to potential energies, but the main idea
transcends any notion of energy, potential or otherwise, and should
be taught separately. If there is a misconception here, associating
it with "potential energy" is an unhelpful blurring of two ideas.

4) In physics and related disciplines, "potential" means positional,
and has been used in this sense more-or-less consistently since
about 1840 (or perhaps earlier; I don't know). This extends to
gravitational potential, electrostatic potential, et cetera. By a
further extension, any functions of state are called thermodynamic
potentials e.g. chemical potential, Gibbs potential, et cetera (which
exist in an abstract state-space, not in prosaic position-space).

Teaching some other name as the "preferred" name does not do the
students any favors.


5) Minor point: "potential" comes from the same root as "potent"
and "potentate" i.e. an ancient root having to do with power and
capability.

I don't know the exact etymology, but I would not be surprised
if the supposed etymology of "potential energy" as latent or
inchoate energy turns out to be entirely wrong (in addition to
being irrelevant, as discussed in item 2).

If students are really stuck on the name, have them think of
"potent" energy or "potentate" energy. I'm not saying those
names are any improvement; indeed I'm saying almost the
opposite: this is a way of pointing out the silliness of
reading too much into a name.