Concepts

Conservation of angular momentum

Overview

A person sits or stands on the rotating stool (or platform) and holds the weights with his/her arms extended. After the stool is spun, the person brings his/her arms closer to the body. By moving masses closer to axis of rotation, the moment of inertia of the system is decreased, so the angular speed of the system must increase in order to conserve angular momentum.

Details

Equipment

• [1] Low-friction stool, platform, or chair
• [2] Weight

Classroom Assembly

1. Place the low-friction platform, chair, or stool on a clear spot.
2. Level the chair, if applicable.
   

Important Notes

• Make sure the person demoing the wheel won't hit anything while rotating and has room to stumble off the platform if it is used.

Script

1. Get a volunteer onto the low-friction apparatus.
2. Hand the volunteer two weights and ask him/her to hold one in each hand with arms extended.
3. Spin up the rotating apparatus.
4. Ask the volunteer to brings his/her arms closer to the body. Notice the increase in angular velocity of the system.

Additional Resources