The angle between the resultant contact force and the normal force exerted by a body on the other is called the angle of friction. Show that, if λ be the angle of friction and μ the coefficient of static friction,

Let us consider, the frictional force to be f,

The applied force= F

Normal reaction= R

Coefficient of friction force =

When the force applied on the body increases, the force of friction also increases. It increases up to limiting friction .

Before reaching to the limiting friction