Question

The limiting friction between two surfaces does not depend:
A) On the nature of two surface
B) On normal reaction
C) On the weight of the body
D) On the height of the body

Answer 1

Hint: Limiting friction is the maximum amount of friction that can be produced between two static surfaces. Only the normal force and surface of the body are responsible for the limiting friction between any two surfaces.

Complete answer:
Limiting friction comes into play when the body is at the point of sliding over the surface of another body, and it is generated due to the irregularities between two surfaces. Limiting friction is the maximum value of static friction divided by the normal reaction force that is perpendicular to the surface. Once the force overcomes the limiting friction, the body is set in motion.
$f = \mu N$
Where $f$ is the limiting friction,
$\mu$ is the coefficient of limiting friction,
And $N$ is the normal force acting on the body.
This formula only applies when the two surfaces are dry.
The limiting friction will depend on the nature of the two surfaces because $\mu$ depends on the two surfaces. As we can see in the formula of limiting friction, it depends on the normal reaction, and as the normal reaction is equal to its weight, therefore the limiting friction does not depend on height or its dimensions. It only depends on the surface of the two bodies.

The incorrect option is (D), on height of the body.

Note: Static friction and limiting friction are two different things. Static friction is a self-adjusting force that acts between the surface of two bodies when there is no movement between the bodies, but when the body overcomes this static friction, it reaches the maximum value of static friction, which is called the limiting friction.