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



Thats not the issue. I completely agree that energy is a construct,
I am just saying that force is no better. I'm not even saying that
one or the other is easier for a child to understand. I would
however be suspicious of their understanding of force simply because
the common examples are so different from the wider range of forces.

Force has been called Newton's embarrassment because he could not
explain it...we still can't.

cheers,

joe

On Aug 17, 2005, at 1:29 PM, Anthony Lapinski wrote:


Perhaps. Okay, what is your definition of energy?

Forum for Physics Educators <PHYS-L@list1.ucc.nau.edu> on Wednesday,
August 17, 2005 at 12:20 PM -0500 wrote:


So what is the basis for a force being more real than energy, since
you can only claim it exists intermittently when the velocity of some
object changes. Some forces, like pushes and pulls may be more
tangible, but the notion of force is deceptive. It is more familiar,
so perhaps more acceptable than energy, but it seems to me, no more
real.

cheers


On Aug 17, 2005, at 8:53 AM, Anthony Lapinski wrote:



Sure. Everyone knows that forces are pushes or pulls. But that often
implies CONTACT
(friction, normal force, etc.). There are also forces that are
FIELDS, and
students know
about these, too (gravity, magnetism, etc.). Since I teach forces
after
motion, I usually
say that a force is any "interaction" that can change the velocity
of an
object. Then I can
discuss Newton's laws and, later, energy.

Forum for Physics Educators <PHYS-L@list1.ucc.nau.edu> on Wednesday,
August 17, 2005 at 8:24 AM -0500 wrote:



On Aug 17, 2005, at 7:00 AM, Anthony Lapinski wrote:





Good discussion on this important topic!

Energy is an important concept in all the sciences. Traditionally,
physics
discussed PE and KE. PE is always associated with a force, and
the KE
equation
is derived from equations from 1D and NL. So it makes sense to me
to talk
about forces first.

I think kids can relate to forces much easier than to energy.
After
all,
energy is not real,
only an abstraction invented by humans to explain things. Ask
anyone for a
good
definition of energy, and you'll get many responses. Ask about
forces, and
it's a no-brainer.




I would be interested in your definition of force...not
referring to
Newton's laws, since that would be circular and your inference is
that somehow force is more fundamental than energy...so don't
define
it in terms of energy either.
Does you definition work for the range of forces we commonly talk
about, ie gravitational, electromagnetic, intermolecular, etc.?

cheers






Energy is also a conserved quantity, which makes it easy to solve
many
problems
in physics.

Forum for Physics Educators <PHYS-L@list1.ucc.nau.edu> on Tuesday,
August
16, 2005 at 7:07 PM -0500 wrote:





Apologies for joining this discussion rather late. I guess I'm
one of
the "some physicists" mentioned below, although I've never taught
high
school or even a standard Physics 101 college course.
However, for
three years I did teach an honors physical science course, with
energy
as the unifying concept, for college students who were not
majoring in
science.

For that course I wrote some text materials which you can
download
from
<http://physics.weber.edu/schroeder/energy/>. Don't get your
hopes
up--these materials are not even close to being a textbook.
Rather,
they're a very terse overview of the core physics that students
were
expected to learn, with a collection of student exercises. In
the
course, these materials were supplemented by additional readings
from a
wide variety of other sources, plus hands-on experiments and
other
activities. By the way, if you read Chapter 2 you'll see that I
did
not (nor was it my goal to) eliminate all reference to force and
work.
However, I did pretty much eliminate acceleration!

Another excellent resource is Bob Romer's old book, Energy: An
Introduction to Physics (Freeman, 1976, unfortunately out of
print).

Without trying to get into an argument with those who feel that
this
approach to physics is idiotic, here is a list of some of the
advantages that I see:

* Energy is a familiar concept in everyday life, tangible
because we
pay for it (in dollars, pounds gained, etc.).
* Energy is an important political issue that all educated
citizens
must understand.
* Energy is a key concept in other sciences: chemistry, biology,
geology, astronomy.
* Energy-related quantities and calculations provide an
outstanding
opportunity to develop students' numeracy skills.
* Energy really is more fundamental than force. While some
particular
forms of energy (gravitational, elastic) are closely related to
force
and are calculated from measured forces, other forms of energy
(thermal, chemical, electrical) are calculated from entirely
different
measurements. Energy in general is a much deeper and broader
concept
than force.

Dan S.







Date: Wed, 10 Aug 2005 12:09:47 -0500
From: Dan Crowe <dcrowe@SOTC.ORG>
Subject: Energy is primary and fundamental? (was RE: First Day
Activities or
Demos)

John,

Some physicists advocate starting a first course in physics at
the high
school level with energy and energy conservation, but I don't
know how
to do that.

How do you define energy without reference to force or work?

How can high school students develop an understanding of energy
and
energy conservation at the beginning of their first course in
physics?

What guidance should a teacher provide in this process?

Daniel Crowe
Oklahoma School of Science and Mathematics
Ardmore Regional Center
dcrowe@sotc.org