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



jbellina wrote:
I gather you are writing that to be real you must directly experience
it without the use of instruments...so a smack in the nose is real.
What then about Africa, or a hallucination...something you alone
experience. Are electrons real, or atoms?

real is tough,


exactly! I would say there is a difference between the experience and
the decription of that experience. The description is necessarily
abstract, in that it does not communicate all of the details. All of
physics is a description of experience. The description is useful if it
makes testable predictions, but the variables in the description are not
"real" in any way. Some have a more straightforward comparison with
experience, but they are still abstractions.

John Denker writes:

I agree that some notion of position is important, but this isn't a
major stumbling block for most students.

Velocity is important. In particular, the distinction between
velocity and speed becomes important at some point ... but you can
compute KE just fine *before* understanding this distinction.

this is much of the reason why I introduce energy early: you can use it,
intuitively, without bringing in acceleration (which is often initially
confused with velocity), and vectors (which take quite a while to
explain).


Perhaps to use the word "fundamental" is not the best one, because it
immediately gives an err of superiority. From my perspective, it's
really an economics problem: given the limited resource
of 1 semester of time, how do you present a view of what physics is?
Some choose to do a couple of topics, in some depth. Some choose to
pack in everything at breakneck speed (which is what I did to start,
before realizing it didn't give much to the students). For me, I want
to cover some modern physics so the students don't walk away thinking
nothing has changed in 100 years.

As an experiment I tried to answer the question, "what is the minimum
number of concepts necessary to teach the most physics". If I
introduce, say, 2 concepts and use them in 20 different contexts, then
the students may come to understand the power of these methods. I
found, empirically, that position, then velocity, then energy, then
momentum carries me very very far. I might not be able to do *every*
example, or even some people favorite examples, but I can do quite a bit
and I think the message comes through. Then, with small modifications
for relativity, all the same techniques done in the first part of the
semester transfer to the next part. I do try to put in some waves (just
simple superposition, and resonance), so I can then cover some about
quantum mechanics.

I like the notion of using symmetries, in which case the course would be
all about symmetries and their consequences.

I certainly wouldn't say that my approach is perfect (or perhaps even
novel), but it has worked for me (and I keep tweaking it).


bb


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bblais@bryant.edu
http://web.bryant.edu/~bblais