Briefly explain the origin of friction show that in an inclined plane angle of friction is equal to angle of repose

Explanation

During the era of Nweton and Galileo friction force considered as one of the natural forces like gravitational force . But in the twentieth century. The knowledege of atoms electron and protons has changed the perspective . The frictional force is actually the electromagnetic force getween teh atoms on the two surfaces .At the microscopic level even well- polished surfaces have irregularities on the surface