Explain Kinetic friction. Write laws of kinetic friction. Define coefficient of kinetic friction.

Explanation

When magnitude of force acting on object lying on surface exceeds maximum static friction the object will start moving in direction of external force. Hence value of friction force will reduce less than maximum static frictional force.

Frictional force which opposes relative motion between surfaces in contact is called kinetic friction it is denoted by `f_(x)`
Laws of kinetic friction
(i) Kinetic friction do not depend on area of contact between surface
(2) kinetic friction force do not depend on relative velocity of object in motion
kinetic friction force is proportional to normal force
`mu_(k)=` coefficient of kinetic friction `mu_(k) = (f_(k))/( N )`
if extermal force applied is reduced to zero then acceleration of object will be be `-(f_(ik))/( m)` Hence it will stop after covering some distance