Demos: 1Q-11 Change in Rotational Inertia
Two weights are held apart by a string which is burned after the system has begun rotating. The weights transfer quickly to the center resulting in a significant increase in the rotational acceleration, demonstrating that a is inversely proportional to I.
Directions: This is best done as a qualitative demonstration, since the timing the two separate motions is quite difficult. With the weights stretched out, let the hanging weight which propels the system fall. Then after a few turns, when the angular acceleration is evident, burn the string. The increase in a will be evident visually.