Question

Explain the two theories of friction

Answer 1

1. Origin of sliding friction (Old View ) :
According to this view, roughness of surfaces is the cause of friction. A surface which appears very smooth to the naked eyes is found to have irregularities (roughness) when seen through a powerful microscope. This is true of every surface.

When two bodies are in contact with each other, the irregularities in the surface of one body get interlocked in the irregularities of the other surface. To move one body over the surface of the other, these interlockings have to be broken. Hence, some force has to be applied. This applied force is a measure of friction between the two surfaces in contact which acts in direction opposite to that of the applied force.

2. Modern view of friction is that it arises on account of strong atomic or molecular forces of attraction between the two surfaces at the point of actual contact