School of Physics Lecture Demonstration Manual

Mi-1 Rotating Stool

Published: Thursday 09 March 2006 - Updated: Thursday 24 March 2011


To demonstrate the conservation of angular momentum.



Click on pictures to enlarge.

Rotating Stool Pic

Rotating stool diagram


Rotating Stool


A volunteer student is seatd upon the stool holding a dumbbell weight in each hand close to the body. The stool is rotated slowly. The student then outstretches his/her arms and the redistribution of mass requires a change in rotational speed to conserve angular momentum.

If initially the student has his/her hands outstretched when the weights are brought in toward the body the increase in rotational speed can be large enough to make it almost impossible to stay seated.

Safety notes


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