Question

What is the difference between rolling friction and sliding friction?

Answer 1

Hint:Rolling friction is experienced by an object that rolls along a surface while sliding friction is experienced by an object that slides along a surface. A rolling body will execute translational motion and rotational motion while a sliding body only executes translational motion.

Complete step by step answer.
Step 1: Describe how rolling friction and sliding friction come into existence.
When an object slides along a surface, at each instant of time only one point of the body will be in contact with the surface. The frictional force that opposes the sliding of the body on a surface is called sliding friction. It is given by, ${f_k} = {\mu _k}N$ where ${\mu _k}$ is the coefficient of sliding friction and $N$ is the normal reaction force acting on the body.
Examples of sliding friction are a child sliding down on a slide in a park or lighting a matching stick by striking the matchstick on a side of the matchbox.
Now when an object rolls, the surface on which the object rolls gets momentarily deformed. This suggests that at each instant of time, it is not a single point but a finite area which becomes in contact with the surface on which it rolls. The frictional force that opposes the rolling of the body on a surface is called rolling friction. It is given by, ${f_r} = {\mu _r}N$ where ${\mu _r}$ is the coefficient of rolling friction and $N$ is the normal reaction force acting on the body.
Examples of rolling friction is a skateboard moving on wheels eventually stopping because of rolling friction and a football rolled on a playground coming to rest because of rolling friction.
Step 2: List the main differences between rolling friction and sliding friction.

Rolling friction	Sliding friction
Occurs when an object rolls on a surface	Occurs when an object slides on a surface or when two surfaces are rubbed against each other
It is due to deformation of the surface as the object rolls on it	It is due to the interlocking between microscopic surfaces
Only a point on the surface remains in contact with the object	A finite area of the surface remains in contact with the object
It depends on the geometry of the object, its weight and on the texture of the surface in contact.	It depends on the weight of the object and the texture of the surface which is in contact with it.
The rolling friction is given by ${f_r} = {\mu _r}N$	The sliding friction is given by ${f_k} = {\mu _k}N$

Note:For the same weight, the rolling friction is less than the sliding friction. So if we were to move a body across a horizontal surface, the movement of the body will be easier if it was placed on a skateboard having wheels than just sliding it across the horizontal surface. This is why the discovery of wheels is such a tremendous milestone in the history of mankind.