Rotating Stool

The moment of inertia is large with the masses held out. For a given angular momentum, the angular velocity is relatively low. If the masses are pulled in, the moment of inertia is considerably decreased. Conservation of angular momentum dictates that the angular velocity must increase.
Demonstration
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Rotating Stool

Begin with the wheel rotating so that its angular momentum is upward. The man and the stool are at rest. The stool is on a bearing mount so that it can freely rotate. If the stool is turned over, its angular momentum is now downward. But since there is nothing to exert a significant torque on the system, the angular momentum must have the original value upward. The man and the stool begin to rotate with angular momentum twice that of the wheel.
Index

Vector rotation examples
 
HyperPhysics***** Mechanics ***** Rotation R Nave
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