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Forces Related to Friction. F f = µ • F n µ = F f / F n µ is the coefficient of friction. F a = Applied force. F f = force of friction. F n. F g =Weight. dragging a box across the floor. Friction is a force. Opposes motion
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Forces Related to Friction Ff = µ • Fn µ= Ff / Fn µ is the coefficient of friction Fa = Applied force Ff =force of friction Fn Fg =Weight dragging a box across the floor
Friction is a force • Opposes motion • depends on the smoothness of the object and the surface it is moving on • depends on the weight of the object • Force of friction = µ x normal force • µ is coefficient of friction • related to smoothness • 0.1 for ice, 0.2 for smooth, 0.5 for rough surface
Measuring force of friction • When block moves at constant velocity, the force of friction equals the applied force • The force of friction opposes the applied force • If the surface is flat, the normal force equals the weight. • The force of static friction is usually slightly larger than the force of sliding friction.
Static and Kinetic Friction • Kinetic Friction • Object is moving • Surfaces are sliding passed each other • Static Friction • Objects not moving • Static Friction balances force of the push