PURPOSE: To demonstrate that centripetal force varies with radius.

DESCRIPTION: Magnets are stuck at three radii on a rotating disc. As the angular velocity is continually increased, the outer magnet flies off first, and the inner magnet last, assuming that the magnetic forces are equal. This is a direct result of the fact that the centripetal force required is proportional to the radius of rotation.

Click your mouse on the photograph above to see an mpeg video of the experiment.

SUGGESTIONS: See Question of the Week #24 for information on using this demonstration to enhance class involvement.

REFERENCES: (PIRA 1D55.30)

EQUIPMENT: Variable speed motorized rotator, magnetic stainless steel disc with three small magnets.

SETUP TIME: None.