Question

Which of the following are ways to INCREASE friction between two surfaces?

P. increase the roughness of the surfaces

Q. increase the smoothness of the surfaces

R. add some oil between the two surfaces

Answer 1

Explanation:

increase the roughness of the surfaces

Answer 2

Explanation:

If the surfaces that are in contact are rough, there is more friction. Hence to reduce friction, the surfaces in contact are kept smooth and polished. It is worth noting that if the two surfaces in contact are of the same metal, the friction increases on polishing the two surfaces. This is why the bearings and the axle are made of different metals.

When we slide two extremely flat and highly polished metal surfaces together, molecular attraction adds to the coefficient of friction. In other words, the coefficient decreases as you reduce roughness up to a certain point where it then increases due to the molecular effects.