The frictional force between two bodies??

The frictional force between two bodies is the force that resists the relative motion or tendency of motion between the two bodies in contact. It is caused by the roughness of the surfaces in contact and the interlocking of the irregularities on the surfaces. The magnitude of the frictional force depends on the nature of the surfaces in contact, the normal force pressing the surfaces together, and the coefficient of friction between the two surfaces.