Question

Rolling friction is always greater than static friction. Is this statement
A. True
B. False

Answer 1

Hint: When the body is on the verge of moving on the surface of another body, the opposing force is called limiting friction. Once the body overcomes the limiting friction, the interatomic bonding between the body and the surface at the point of contact breaks, and the surface becomes comparatively smoother.

Complete step by step answer:
Friction is an opposing force that comes into play when one body moves or tends to move on the surface of another body.
1. Static friction: It is that opposing which comes into play when one body tends to move on the surface of another body but the actual motion has not yet started.
2. Kinetic friction: It is that opposing force which comes into play when the body actually moves on the surface of another body
- Rolling friction is a type of kinetic friction; it comes into play when one body actually rolls on the surface of another body.
- According to the modern view, the friction between two bodies is due to the interatomic force of attraction between the body and the surface of another body at the point of contact. This phenomenon is called cold welding.
- The maximum opposition offered by the interatomic forces is known as limiting friction (limiting friction is maximum static friction). When the external force becomes greater than the limiting friction, the interatomic bond breaks and the surface becomes comparatively smoother than before. Hence kinetic friction is less than static friction. As rolling friction is a type of kinetic friction, it is also less than static friction.
Therefore, rolling friction can never be greater than static friction.

So, the correct answer is “Option B”.

Note:
Students should be aware of the laws of limiting friction and understand the concept of friction and its types. You should not get confused between static and sliding friction. Keep in mind the dependence of friction on area. Rolling friction is the weakest type of friction, static being the strongest. The frictional force depends on the area of contact between the two bodies. As the area of contact is less in rolling friction than the sliding friction, so rolling friction is weaker than sliding friction.