Question

At what conditions does the Coulomb friction occur between the surfaces in contact of collar bearings or pivots?

(a) When there is no lubricating fluid

(b) When there is no friction fluid

(c) When there is no adhesive fluid

(d) When there is no cohesive fluid

The question was asked during an internship interview.

My question comes from Frictional Forces on Collar Bearing, Pivot Bearings and Disks topic in section Friction of Engineering Mechanics

Answer 1

The correct answer is (a) When there is no lubricating fluid

Explanation: When there is no lubricating fluid present between the surfaces in contact, the dry friction occurs. Thus as the name suggests dry friction. When there is no liquid present over there the surfaces are going to be said dry only. Thus the term dry friction.