[Phys-L] Re: Energy is primary and fundamental? (was RE: First Day Activities or Demos)

[rmcder at PEOPLEPC.COM (R. McDermott)]

Bearing in mind that we're discussing how one would introduce energy
early/first in a physics course,
I'd be interested in hearing how you would explain energy in a non-"voodoo"
way.  For that matter, how you explain energy by discussing work.  Imo,
every approach I've ever seen in handling the concept of energy has holes
you could drive a truck through, but maybe you have some approach that is
unique.  I'd appreciate some elaboration.  Do you discuss "energy" at any
point in your course?  Aren't the problems in conceptualizing THEN the same
as the problems at THIS point?

----- Original Message -----
From: "rlamont" <rlamont@POSTOFFICE.PROVIDENCE.EDU>
To: <PHYS-L@LISTS.NAU.EDU>
Sent: Wednesday, August 10, 2005 6:12 PM
Subject: Re: Energy is primary and fundamental? (was RE: First Day
Activities or Demos)


> This approach seems too much like some form of "voodoo" to me.
> Ascribing some poorly defined entity called "energy" to anything
> that is thought of as change is too close to the pseudoscientific
> babble we hear from people who believe in ESP, faith healing,
> homeopathy, etc. If you have no concrete explanation for a
> phenomena you say some form of "energy" is transferred from one
> object to another.

Let's start here..  What exactly do you mean by the expression "form of
energy", and what would you propose we use other than the "poorly defined
entity called energy"?

> Of course, in most cases, that energy cannot
> be seen or sensed - or measured.

Could you provide a specific case?

> If I was a student just encountering physics, I would be very
> turned off on the subject if introduced to it with this
> nonspecific mumbo jumbo.

May I point out that you would have been introduced to energy "mumbo jumbo"
at a much earlier age, and would probably feel comfortable about using the
terminology although your understanding of it is probably inaccurate, poorly
constructed, and extremely limited?  This would NOT be your first exposure
to the terminology!  Students come into my class absolutely certain that
when potential energy (whatever that is) decreases, kinetic energy (they
know what THAT is, although they don't recognize that there are different
modes of motion) must increase.  That and that we need to "conserve energy"
(meaning save it up for the future).

So far all you've done is to criticized the Modeling approach to handling
the concept of energy.  How about offering something concrete as a superior
alternative, and I'll see if I can pick some holes in it?

> Bob at PC
>
> > Dan,
> > The Modeler's definition of energy is somewhat different from
> > the classic "energy is the capacity to do work", which requires
> > you to define work and, as a result, drag in the discussion of
> > force.  Instead we have something on the order of "energy is the
> > capacity for change", so the emphasis is on the location(s) of
> > energy and the specific changes that occur as a result of an
> > energy increase or decrease.  An energy change can result in
> > changes in motion (kinetic energy change), positioning
> > (potential energy change), arrangement (potential energy
> > change), etc.  Working, radiation, and heating only come in at
> > the stage where one becomes concerned about HOW energy
> > transfers from one thing to another.  All of this allows you to
> discuss energy right away if you think it's appropriate.
> > Note that this approach pretty much requires that fields be
> > considered as "objects" rather than theoretical constructs,
> > since for the Modeler, energy always has to reside
> > "somewhere", and my personal approach to this is to
> > liken fields to springs or rubber bands whose geometry
> > changes as energy changes.  That's a lot farther down the
> > road, of course, but it is a bridge one has to cross eventually
> > if one is to be consistent.