State the laws of friction.

Explanation

(a) Limiting friction depends on the nature of the surfaces in but not on the surface area as long as normal reaction remains the same.
(b) Force of friction always acts tangential to the surface and opposite the direction of motion.
(c ) The limiting friction is directly proportional to the normal reaction between two surface in contact.
(d) The kinetic friction becomes constant, once there is a relative motion between the two surfaces.
(e ) `mu_s gt mu_k gt mu_r "where" mu_s,mu_k and mu_r` are coefficient of friction due to static friction , kinetic friction and rolling friction respectively.