Rotating Stool And Weights
To demonstrate conservation of angular momentum.
Rotating stool with weights.
BE CAREFUL. A subject can easily be rotated off the stool.
A subject sits on the stool, with his or her arms extended, holding the weights. After the system is set into rotation, the subject pulls the weights in to his or her chest, decreasing the moment of inertia of the system and thus increasing the angular speed of the system.
H.W. Dosso, R. H. Vidal, Simple Apparatus for Angular Motion Demonstrations, AJP 30, 528-529, (1962).