Date: Thu, 28 Sep 2000 08:56:26 -0700

Author: Ron Ebert

Subject: RE: Classroom demonstrations: education or entertainment?

Post:

At 10:31 AM 9/28/00 -0500, Laurent Hodges wrote:

>Another demonstration: Once on an out-of-town trip I met by accident a
>student I'd had about 20 years before. He immediately recalled the
>pleasure demonstrations had given him and said his favorite was the
>mechanical analog of the Doppler effect. On this one we have a long, long
>motor-driven string across several tables, moving in a loop about a pulley
>at the far end. We have white paper "riders" (long slender pieces of paper
>folded at the midpoint) that can be dropped at regular intervals (using a
>metronome) while the demonstrator stands still, moves with the string, or
>moves in the opposite direction, to model the change in wavelength. I
>remember being a little surprised that he remembered that particular
>demonstration so long afterwards, but apparently it made quite an
>impression on him.

From time to time, instructors tell me of meeting former students of a
decade or more ago. Invariably, it's the more impressive demonstrations
that are remembered. A favorite that's come to light this way a few times
is the bowling ball pendulum. It seems to make a lasting impression. Even
after such a long time, these former students are still amazed that the
bowling ball didn't hit the instructor's chin.

I've come back from vacation in the middle of this discussion. Maybe this
ground has already been covered, but while we all know anecdotal evidence
for the effectiveness of demonstrations (if they're handled appropriately
in the class), I'd like to see some controlled studies. I could have used
them some years ago when one of our retiring instructors gave us a lot of
humbug about the worthlessness of demonstrations. We also have a small
minority of instructors who use very little or no demonstrations.

Ron Ebert
UCR Physics Department
ron.ebert@ucr.edu
http://phyld.ucr.edu

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