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ACTIVITY 10 (if you have a motion detector)

Hello Kip;                                               11/23/94

Thanks for nice words. Since your "productive sessions currently deal
with interfacing experiments using Vernier" I may suggest the following
modification of the previously described demo. I am referring to the clamped
saw experiment. Place the oscillating end of the saw (or a long plexiglass
blade loaded with an extra mass to reduce frequency) in front of the
motion detector, and record data. It works fine from a distance of about
60 cm; a board taped to the blade may be needed if it is not wide enough
to reflect probing waves. Two tasks can be assigned; (a) show how the
amplitude decreases versus time (curve fitting may be added to this),
(b) show how natural frequency depends on the orientation of the blade
(for example, students may discover that it is 0.8 Hz when the blade is
pointing up, 2 Hz when it is pointing down, and that changes are gradual
between these two extremes).

There will be a detailed article about a study of resonance of a clamped
blade (not with a motion sensor) in a future issue of American Journal of
Physics (by Dorner, Kowalski and Stein). The article was accepted and will
be printed in February or in March of 1995. But do not wait for it; just
start playing and new ideas will keep popping up one after another. Ask for
advice if needed.

     Happy Thanksgiving to everybody. I am glad I am not a turkey.

         Ludwik Kowalski       kowalski@apollo.montclair.edu