1Q40.10 - Rotating Chair with Weights
Demonstrate the conservation of angular momentum.
The "Rotating Chair with Weights" sits on a wheeled movable base and is covered in a plastic dust cover. Remove the cover and wheel the appartus into its position in the classroom in front of the lecture bench. Remove the weights and set aside. Tip the chair over onto its back to be able to remove the wheeled base. There are three plastic cups that mount on the metal screws at the base of the chair (these are necessary for lecture hall use). Place one cup on each screw and carefully bring the chair back to its upright position. You may have to adjust the screws so that the chair is level and doesn't turn on its own. Once it is level, one may sit on the chair and buckle themselves up for a fun, safe ride.
For this demonstration, use the seat belt. The demonstrator, holding a 5- or 10-lb weight at arm’s length in each hand, starts into slow rotation on the chair or the platform. Drawing the weights toward the body increases the rotation rate. If the arms are extended again, the rotation will slow down. The demonstrator can usually feel a Coriolis force, i.e. one is required not only to exert a radial force to pull the weight in, but a force perpendicular to this one in order to make the weight follow the radial path.