FRICTION

EXPLAIN

When a body tends to move under the action of an external force then some resistance will act opposite to the direction of motion between the contact surfaces.This resistance is known as friction or frictional force.

In the other words , friction is the force that will act between two contact surface opposite to the direction of motion.

                                                     

                                                    F.B.D OF BLOCK

R is the normal reaction [because it acts perpendicullarly]

S = resultant reaction

S = (F² + R²)^1/2

φ = The angle made between normal reaction & resultant reaction it is called the angle of friction.

tan φ = F/R = μ = co – efficient of friction.

F = μ R