Introduction to Friction

• Friction

Friction is the force distribution at the surface of contact between two bodies that prevents or impedes sliding motion of one body relative to the other. This force distribution is tangent to the contact surface and has, for the body under consideration, a direction at every point in the contact surface that is in opposition to the possible or existing slipping motion of the body at that point.

A force is applied to body sliding on the floor. After sometime, the force is removed, but the body keeps moving, since it has already attained the velocity. However, after some time the body comes to rest. It is the frictional force, which causes body to stop. If the frictional force were not there, body would have kept moving.

• Application of Friction

In this lecture, few applications of friction are presented.

Wedges

Wedges are small pieces of material with two of its opposite surfaces not parallel. They are used to lift heavy blocks, machinery, precast beam etc., slightly, required for final alignment or to make place for inserting lifting devices. The weight of the wedge is very small compared to the weight lifted. Hence, in all the problems, weight of wedges may be negleted. The following figure is showing a wedge: