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[Phys-L] Re: Energy is primary and fundamental?



----- Original Message -----
From: "jbellina" <jbellina@SAINTMARYS.EDU>

Sorry Jim, you are missing my point. It is not that energy is real,
rather it is that force is no more real then energy, so you can't
privilege it on that basis.

joe

Of course, Joe isn't real either!

We constantly go around on this point, but to the majority of our students
forces AND energy are definitely real. They have the experiential
background of pushes and pulls (even if we want to nit-pick that this
experience is really impulse). They intellectualize energy as a real
thing--they pay for it (and pay for it) at the gas pump and feel it at the
beach.

The fact that theoretical physicists would describe 'forces' in terms of
interacting fields or that energy is just a mental construct that we've
invented to track a certain class of measurable changes is fine to mention
and important to pursue in advanced courses, but for most intro courses we
need to keep these things 'real' for the students.

That being said, the main issue here is pedagogical--whether to start with
kinematics/dynamics or with energy. With the 'reality' of force and energy
in the student's minds as a consideration, I would still choose to go the
kinematics/dynamics route because the phenomena and the concepts seem more
accessible to students. That is, motion in general, pushes and pulls, and
the phenomena normally explained by Newtonian mechanics is familiar and
reproducible--especially in intro labs. Kinetic and potential energy, while
based on motion and position, are still at least one step more abstract to
students than velocity and forces. To be sure, acceleration is tough, but
as someone else pointed out, dealing with kinematics and dynamics quickly
introduces the importance of direction into the formal study, something that
energy does not. [Some may view that as a plus for energy first.]

In the end, it still comes down to your goals for the particular clientele
you are teaching and how effective you judge you are being with one approach
or another--properly measured, of course! ;-)

Rick

*********************************************************
Richard W. Tarara
Professor of Physics
Saint Mary's College
Notre Dame, Indiana
rtarara@saintmarys.edu
********************************************************
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NEW: Energy Management Simulator
www.saintmarys.edu/~rtarara/software.html
Energy 2100--class project
www.saintmarys.edu/~rtarara/ENERGY_PROJECT/ENERGY2100.htm
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