Torsional Oscillator Demonstration Part 1

A dumbbell is suspended from its center by a wire, and can undergo rotational oscillations due to the twisting of the wire. The oscillations are observed to be very weakly damped. The period is measured to be independent of the amplitude, including very small amplitudes that are seen by reflecting a laser beam off an attached mirror to a distant whiteboard. Hitting the table by hand causes higher-frequency perpendicular oscillations that damp out in time. An approximate theoretical determination of the period agrees with the measured period. Finally, to reduce the moment of inertia, the dumbbell masses are moved much nearer to the wire, which is observed to substantially decrease the period.
Prof. Bruce Denardo
Videographer Mr. Gene Morris
Physics Department
Naval Postgraduate School
Monterey, California