Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: [Phys-L] let's define energy

I look at the title of this thread and I can't help thinking: Let's NOT define energy. Let's just define specific energy types. We have these interesting quantities. Under a particular set of circumstances, each can be shown to be changed by work. So for example, we could call (1/2)mv^2 the "work-changed motion-related quantity". Call mgh the work-changed height-related quantity. Build your collection. Then show how together, these quantities follow a conservation law. (And when they seem not to, it means we have overlooked another member of the family.)

At the end of teaching this, you could mention (or not): Oh, by the way...collectively, these are all called "energy".

Would you meet your state standards? I don't know. Would you be doing harm? I don't think so.

On 9/28/2015 5:09 PM, Paul Nord wrote:
They seemed to think that it went deeper than simply the difference between
vernacular and technical definitions of energy. The energy vs. entropy
usage is one difference in the sciences. You listed some others.

As physicists we all agree that you just need some unit changes to make all
of these systems compatible. But we still speak of energy as an abstract
concept, as a material property, as an object, or as a thing which flows
and may change form. Scientists are not very consistent with the words
they use for speaking about energy.

Paul

On Mon, Sep 28, 2015 at 3:56 PM, John Denker <jsd@av8n.com> wrote:

On 09/28/2015 10:59 AM, Paul Nord wrote:

Also from that session Rachel Scherr provided a nice overview of the
discussions of forms of energy given by various state standards.
[...]
She mentioned standards in several states where they have interesting
acronyms to memorize the forms of energy: SCREAM - Sound, Chemical,
Radiant, Electrical, Atomic, Mechanical
It's refreshing, in a morbidly-fascinating sort of way,
to see the states being so upfront about their emphasis
on rote memorization to the exclusion of understanding.

Consider for example a hot potato in contrast to a cold
potato. The energy is different, but not in a way that
fits into the SCREAM scheme. Anybody who understood the
subject would notice this immediately.



I particularly recommend looking for anything Stamatis Vokos wrote on the
subject.
OK, wow, that's interesting. Thanks for the pointer!
I found this:
[1] http://spu.edu/depts/physics/EPPublications.htm
and more particularly this:
[2] http://spu.edu/depts/physics/documents/Daane.PhysRevSTPER.10.pdf
on which both Scherr and Vokos are among the co-authors.

His philosophy is quite deep, so I wouldn't pretend to understand
everything he said.
Well... if you have trouble making sense of reference [2]
(above), congratulations, that means you're smart and
paying attention. Much of it simply doesn't make sense.

The paper claims to adhere closely to the Next Generation
Science Standards. That's bad, because there's a lot of
nonsense in the NGSS.

In particular, they try to explain in terms of energy a
whole host of things that can be understood in terms of
/entropy/ and not otherwise.

Furthermore, they trample on the distinction between the
physics energy and the vernacular «energy». These are
both important concepts ... they're just not the same
concept.

I realize that on a daily basis teachers and students
need to deal with the state standards as they are, not
as they should be. However, at some point, somebody has
to say /Eppur Si Muove/. The authority of the state
cannot overturn the laws of physics.

Now I begin to understand why they are having a hard time
defining "energy".
1) As long as they don't recognize the distinction between
physics energy and vernacular «energy», they are going to
make life miserable for themselves and everybody else.
2) As long as they try to use energy to explain stuff
that can be understood in terms of /entropy/ and not
otherwise, they are going to make life miserable for
themselves and everybody else.
*) There may be other issues that I haven't picked up on.

Interesting discussion!

These are fixable problems! Explaining the distinction
between physics energy and vernacular «energy» is a
challenge, but failing to explain it is a fiasco.

_______________________________________________
Forum for Physics Educators
Phys-l@www.phys-l.org
http://www.phys-l.org/mailman/listinfo/phys-l

_______________________________________________
Forum for Physics Educators
Phys-l@www.phys-l.org
http://www.phys-l.org/mailman/listinfo/phys-l