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Re: Energy, etc (fwd)



Folks, at this point in the development of some sort of correct language, I
would applaud _any_ language which steers the students (and ourselves) away
from the cartoon physics which is taught in grammar school and on Bill Nye
the Science Guy (where, for example, one engineer says "tons of energy
flows down" a pipe) and on the evening news. The modifiers "level" or
"magnitude" or "intensity" or in deed "energy" alone will require some
sort of precept that energy is a _property_ OF a body or system and not a
separate substantive material which moves independently from the
system. For example I surely would not say "amount" of energy. I would
even be careful in this world of mis-educated students of saying that the
system "has" energy without some sort of caveat.

Jim Green


I have a problem or two with "magnitude". The term is usually
associated with vector quantities, though it is itself a scalar,
a minor drawback, but it also implies the existence of some sort
of canonically mandated zero of energy when what we really want
the students to concentrate on is energy differences. There is,
of course, a natural zero for energy, but we wouldn't want our
students adding in the mc^2 terms in a roller coaster problem,
would we?

Why can't we say "the energy" and define it somewhere else? That
is what we do with the entropy (which also has a natural zero)
when we teach them about it.

A student's introduction to these quantities should be as
symmetrical as Clausius perceived it to be:

Energy is a function of the parameters which define the state
of a system. It is measured relative to a conventional zero.

Entropy is a function of the parameters which define the state
of a system. It is measured relative to a standard entropy.

Leigh

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