Demos: 1Q-22 Conservation of Angular Momentum (Compressed Springs)

This demonstration is very similar to 1Q - 20, except that the spheres may be pulled inward or pushed outward, by the arrangement of springs. In the first arrangement, the sliding spheres are held against compressed springs by a string. After the system is set into rotation, the string is cut or burned and the spheres are projected outward along the rod, increasing the rotational inertia. In the second set-up, the strings attached to the spheres are passed under and over pulleys at the end of the rod and then tied together so that the springs are now stretched. When the system is set into rotation, the string is again cut or burned, causing the spheres to move quickly toward the center, decreasing the rotational inertia.

Directions: The directions are self-evident in the description above. Be careful that you not hit yourself with the rotating rod while cutting or burning the string.

Suggestions for Presentation: This demo is part of a series that illustrate conservation of angular momentum. Focus on the fact that the forces are internal and do not contribute to a change in the net momentum of the system.

Applications: As with the others in this series, there is some connection to spinning ice skaters, divers, etc.

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