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Nonetheless, I think that there is a complementary role for computer
demonstrations. Students have to understand our interpretations before
they can be convinced that they do or do not describe nature. As an
example from classical physics, last night I held a help session for an
exam tomorrow in a calculus-level introductory course. One of the
students was puzzled about circular motion, the usual "why am I pushed
outward?" Now I had 1) Spun a cork on a string and shown that it went
straight when I let go "I know that the object goes straight when you
quit pushing on it, but ..."; 2) Talked about what causes the nerves in
our muscles to fire and give an impression of an outward force, and why;
3) worked several problems from stationary frames; 3) shown how a block
on top of a second block appears to fall backward when the lower block
is accelerated but really goes forward; 4) even got the entire class to
chant the direction of the force (they memorized the answer I wanted but
didn't believe it, of course); etc. ad nauseum. We are all used to this
phenomenon.
So last night I hauled the entire class to my office and showed them a
computer program which shows two things: First, the path of an
unaccelerated moving object on a merry-go-round as view from above in
the stationary and in the rotating frame; and second, the path followed
in the stationary frame by a object which is acted on only by a series
of hammer blows. Bingo. The picture of an object going around in an
essentially circular path made up of many short-line segments between
points where the object was kicked inward did the trick, for all of
them.
--
Maurice Barnhill, mvb@udel.edu