PURPOSE: To demonstrate that the coefficient of static friction is greater than the coefficient of sliding friction, and to determine the coefficient of static friction.

DESCRIPTION: Position the block on the incline and slowly increase the angle until the block begins to slide down the incline. Because the coefficient of static friction is greater than the coefficient of sliding friction, after the block starts sliding it will continue to slide.

The coefficient of static friction is equal to the tangent of the angle at which the sliding commences.

SUGGESTIONS:

See Question of the Week #132 for information on using this demonstration to enhance class involvement.

REFERENCES: (PIRA 1K20.35)

EQUIPMENT: Inclined plane with wood block, as photographed.

SETUP TIME: None.