What is the origin of frictional forces?

A disc spinning clockwise about its axis with angular velocity omega_0 is set on a rough horizontal plane[Fig.]. What si the direction of frictional force at point P and sense of frictional torque ,before pure rolling starts? .

Supose your writing desk is tilted a little. A book kept on it starts sliding down. Show the direction of frictional force acting on it.

Suppose your writing desk is tiltrd a little .A book kept on it starts sliding down. Show the direction of frictional force acting on it.

A disc spinning clockwise about its axis with angular velocity omega_0 is set on a rough horizontal plane[Fig.]. What is the force of friction after rolling without slipping starts? .

What is force?

Explain why friction is necessary to make the disc roll in the direction indicated. Given the direction of friction force at B, and the sense of frictional torque, before perfect rolling begins.

A stone of 1 kg is thrown with a velocity of 20 ms^( -1) across the frozen surface of a lake and comes to rest after travelling a distance of 50 m. What is the force of friction between the stone and the ice ?

What is meant by origin of replication?