Friction

Friction is the resistance to motion that is set up while one body slides over another. In several instances it is a source of trouble. This means in every machine some energy must be utilized to overcome friction at the place where surfaces slide over each other. By utilizing a lubricant such like oil or grease among the surfaces, the frictional force might be reduced but never removed so it seems friction is undesirable, wasteful of energy and expensive in terms of the wear it makes and the power expanded to overcome it. However there are several situations in which friction plays an vital role.

The force known as friction might be defined as the resistance encountered by one body in moving over another.