JAMB Physics 2019 Paper

Concept:Limiting friction is the maximum frictional force that opposes motion just before sliding begins.It is given by $F_s = \mu R$, where $\mu$ is the coefficient of friction and $R$ is the normal reaction.Explanation:The limiting frictional force depends on the normal reaction $R$ between the two surfaces in contact.It also depends on the nature of those surfaces, such as how rough or smooth they are.This roughness is measured by the coefficient of friction $\mu$.So $F_s$ depends directly on both the normal reaction and the nature of the surfaces.The limiting frictional force does not depend on the area of contact between the surfaces.It also does not depend on the relative velocity between the surfaces.Hence, the factors involved are the normal reaction and the nature of the surfaces.Answer:B. I & IV only