PURPOSE: To illustrate centripetal force.

DESCRIPTION: When the ball is rotated around your head in a horizontal circle, the spring extends. This demonstrates that the spring is under tension, showing that a force is required to move a mass in a circle. Rotating faster requires a greater centripetal force, as observed by the greater spring extension.

SUGGESTIONS:

REFERENCES: (PIRA unknown.)

EQUIPMENT: Mass on spring, as photographed.

SETUP TIME: None.