Question

Sliding friction is .................. than rolling friction. fill in the blank.
A. Greater
B. less
C. same as
D. can’t say

Answer 1

Hint: When an object is in contact with the smooth surface the contact force acting on it will be normal force only. When the object is in contact with a rough surface then the contact forces acting are normal force and friction force. Based on surface conditions also frictional force varies.

Complete step by step answer:
Basically there are 4 fundamental forces in nature. Hence whatever the force we talk about, that must be derivative of one of these 4 fundamental forces. Now the friction force is a type of contact force which arises due to interlocking between the surface and the object. It comes under the category of electromagnetic fundamental force which arises due to interaction between the atoms of contact surface and the resting base of the object.
Sliding friction arises when an object is sliding on the surface. When an object is sliding on the surface the area of interaction between the surface and the base of the body will be high. Hence interlocking will be high. Hence friction will be high.
Now when the surface is rolling the area of interaction between the base and the surface will be less hence rolling friction will be less than sliding friction as interlocking is less.
Thus, sliding friction is greater than rolling friction.

So, the correct answer is “Option A”.

Note:
Some tell that the friction doesn’t depend upon the area of contact. The coefficient of sliding friction is experimentally found to be greater than the coefficient of rolling friction. So for the same normal force rolling friction will be less than the sliding friction as friction is a product of normal force and coefficient of friction. Either way sliding friction is greater.