Today, we watch some imaginative teachers at work.
The University of Houston's College of Engineering
presents this series about the machines that make
our civilization run, and the people whose
ingenuity created them.
The other day I passed a
colleague's office and found him stretching a
length of key chain out on his desk. He let part of
it hang over the edge and then released it. The
chain gathered speed and slid off onto the floor.
He timed its fall and then hurried to class. He
asked his students to predict how long the chain
took to slide off. The students were fascinated
because they were called upon to predict reality --
a fresh reality -- a reality that not even their
teacher had yet mastered. It had the imperfections
of reality. How important was friction? Did the
chain slide straight, or was there a wavy movement?
The next day I passed again. He was writing the
experiment up for a journal called The
Physics Teacher. He'd caught the students'
interest, and he was going to share it. I looked at
his copy of the journal to see what else was in it.
One article was by a teacher who watched
MacGyver on TV. In case you don't
know, the MacGyver character used an encyclopedic
knowledge of science to get out of scrapes in prime
time. In one episode, MacGyver had been poisoned,
and the metal container of antidote had slipped out
of reach down a storm sewer. He saved himself by
beating a metal rod to induce magnetism in it. Then
he lowered the rod on a string to get the antidote.
The author talked about the process and, finally,
gave the script his blessing.
I turn the page. Here's another University of
Houston professor with a board across his head. An
assistant is hammering a nail into it. The man's
head is hardly bumped. The students are asked to
This inventory of examples is a celebration of the
classroom at its best. I also have tricks like
these up my sleeve. I like to show how a rubber
band shrinks when you heat it and then ask my
thermodynamics students to make sense of that
This sort of thing might look frivolous, but it
lies at the heart of understanding science. Between
knowing the formalisms of science and really
feeling them in your bones lies a huge chasm. Many
students never learn to cross that chasm, and a few
teachers don't care if they do.
Science is turned from alien mystery into a living
companion only when formal rules take an active
role in explaining nature. That's why Richard
Feynman's famous experiment with the Challenger
O-ring was so powerful. When he dipped a pliant
little rubber ring in ice-water and it turned
rigid, brittle, and useless before our eyes, we
suddenly knew in a deeply personal way why
astronauts had died. True learning takes place when
a student becomes a participant in using science to
master a mysterious commonplace world.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
Faucher, G., Ferromagnetism and the Secret Agent.
The Physics Teacher, January, 1988, pp.
The instructor with the sliding chain experiment is
Professor James Casey, Mechanical Engineering
Department, University of Houston. He was teaching
the junior level course, MECE 3336, Mechanics II.
(Since this episode was aired, Casey moved to The
University of California at Berkeley.)
Casey's equation for the chain's movement is:
x\b = c\b + (1 - c\b) cosh (nt)
t = the time after sliding begins
x = the length of the chain hanging over the end at
b = the length of the chain hanging over the end
when t = 0
c = the maximum length of chain that can hang over
the end without starting the chain into motion.
c = fL/(1 + f)
f = the moving coefficient of friction
L = the overall length of the chain
n = [(1 + f)g\L]½
g = the acceleration of gravity
The instructor with the
nail-in-the-board experiment was Professor Tom
Hudson, University of Houston physics professor and a
gifted user of demonstration experiments. His article
on the experiment is in the journal cited above.
The Engines of Our Ingenuity is
Copyright © 1988-1997 by John H.
Episode | Search Episodes |