Inverted Pendulum

A physical pendulum finds stability in its inverted position when driven at the proper frequency and amplitude combination.

The physical pendulum seen here is mounted on a ball-bearing pivot and can rotate 360 degrees; the pivot is driven at about 50 Hz with an amplitude of about 1 cm (3/4" per stroke) by a Sears Craftsman Auto Scroller Saw (model 315.172090); the length is 45 cm and the center of mass is slightly above 15 cm from the pivot; the rotational inertia is roughly 4x10^(-4) kg*m^2; the mass is about 100 grams.

For more details and references for further study see: http://sciencedemonstrations.fas.harvard.edu/icb/icb.do?keyword=k16940&pa... 

 Shot in 24 and 300 fps. Thanks to Rob, Fu, and Daniel for their help.