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Re: Simple explanations. Was: what are the labs for?



On Sun, 8 Feb 1998, Rick Tarara wrote:

Let me respond with my very first thoughts on this. WHO CARES?

Well, a lot of my high school 'general' physics students care!
I've used the falling slinky demo as an attention getter as well
a fine axample of center of mass motion, free fall etc. (important
CONCEPTS even for the less mathematically advanced HS students.)
The falling slinky also demonstrates that TIME is required for
information to propagate. (The bottom loop of spring can't 'know'
that the top has been released until some time has passed. Calculating
this time delay for a non-uniformly stretched spring is beyond our
syllabus, but he EXISTANCE of the time delay is important, especially
as we approach our CONCEPTUAL treatment of special relativity.


So I posed two simple demos, easy and inexpensive to do. And if teacher
and student see these and aren't surprised and intrigued by them, then
they aren't seriously in the game. They challenge our understanding. If
our "simple understanding" of force and motion can't deal with these, then
maybe it wasn't very powerful or useful understanding after all. It may
even have been wrong. What's the use of understanding which can't be
successfully applied to *new* experiences, even ones you don't happen to
care about? And what relevance does "caring about" something have to do
with it anyway?

I had another motive. To challenge those who crow about how they
teach "conceptual physics" and who emphasize "simple" explanations over
mathematical ones. I wonder, sometimes whether it's all smoke and
mirrors accomplishing nothing but a feel-good *illusion* of understanding.
Perhaps it includes some of the "lies" we've been talking about lately.

Oh, yes. These two examples *do* demonstrate aspects of physics which are
applicable in many other situations.


-- Donald

.....................................................................
Dr. Donald E. Simanek Office: 717-893-2079
Professor of Physics FAX: 717-893-2048
Lock Haven University, Lock Haven, PA. 17745
dsimanek@eagle.lhup.edu http://www.lhup.edu/~dsimanek
.....................................................................
I THINK that I am gaining some insight on the rubber band experiment
by again considering the Center of mass of the 'initially'
uniformly stretched band. Because of the 'time delay concept
mentioned above, it won't be uniform after release. Following the
center of mass motion may again prove to be a useful CONCEPT.
Thanks for the conceptual teaser!

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