A : Work done by friction can increase the kinetic energy of the body.
R : Friction is a type of contact force and it always opposes the relative motion or tendency of relative motion.

Work done by kinetic friction can be

Does friction always oppose the motion?

Does friction always oppose the motion?

A : Work done by the frictional force can’t be positive. R : Frictional force is a conservative force.

A : Work done by the frictional force can’t be positive. R : Frictional force is a conservative force.

The work done by kinetic friction on a body :

The work done by kinetic friction on a body :

Frictional force always opposes motion of a body.

(A) : Friction force always opposes the motion ( R) : Friction force can not support the motion

(A) : Force of friction applied by ground on the wheels of a bicycle is always in the direction of motion of the bicycle . (R) : Force of friction always opposes the relative motion between the surfaces in contact .