In his 10/212/98 Phys-L post of the above title, Mike Moloney writes:
"Sounds like they ....(window sash weights)... would fit inside 1 1/2
inch PVC pipe to make a version of the demo where mass is concentrated
at the center of one pipe while in another pipe the mass is out at the
end. Since they already have holes in the ends, one need only drill
through the pvc
at the right spot."
Such a "demo" is described by Halliday & Resnick in "Fundamentals of
Physics," 4th edition on p. 296. Of course, in order for students to
obtain a kinesthetic appreciation for the moment of inertia (I) and
relate it to Newton's Laws, they themselves must rotate the tubes, think
about what's going on, and relate it all to Torque = I (angular
acceleration). For a Socratic Dialogue Inducing (SDI) implementation
see SDI Lab #4 "Rotational Dynamics," Sec. III "Rotational Motion
Puzzles," "Mystery Batons".
As indicated in the AAPT Announcer, 28 (3), 84 (1998), an SDI Lab
Workshop (W18) will be given at the AAPT Anaheim meeting on Sunday, Jan.
10, 1999, 8:30am - 12:30 pm. Participants will work through SDI Lab #3
versions of popular lecture demonstrations: (a) swinging a bucket of
water over the head, (b) rotating a conical pendulum around the body,
and (c) slipping a tablecloth out from under dishes.
Richard Hake, Emeritus Professor of Physics, Indiana University
24245 Hatteras Street, Woodland Hills, CA 91367
<hake@ix.netcom.com>
<http://carini.physics.indiana.edu/SDI/>