Rolling Friction - Definition, Examples, Coefficient, Causes, FAQs

Edited By Vishal kumar | Updated on Sep 24, 2024 01:38 PM IST

We all know that it is very difficult to pull a heavy almirah on a rough floor. But, if we attach four iron wheels to the bottom of that almirah, then it becomes much easier to push or even pull it. The iron wheel or any of those wheels does not slide on the floor. However, wheels roll on the floor.

This proves that the surface of the wheel which is in touch with the ground does not rub against the ground and hence doesn't slide on it.

The velocity of the given point of contact of the wheel with relation to the floor remains zero, and hence, the wheel keeps moving forward.

What is Rolling Friction?

The force that resists the motion of a rolling body on a surface is called rolling friction.

Rolling of the football,tennis ball or even a wheel on the ground are examples of Rolling friction.

Another type of friction is known to be sliding friction. In such a type of friction, there are restrictions on the given body’s movement as only one side of the body gets in contact with the surface.

Pushing a box is an example of sliding friction.

Rolling friction is a little weaker than sliding friction.

It is usually not always necessary that a wheel or even a sphere will roll. It may also slide depending upon its motion, and also the forces acting on it. Sometimes, just to reduce energy losses due to friction, small steel balls are included into the rotating parts of the wheel machines that are known as the ball bearings.

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Rolling Friction - Definition, Examples, Coefficient, Causes, FAQs

Laws of Rolling Friction

There are basically three laws of rolling friction:

•The force of rolling friction decreases with an increase in smoothness

•Rolling friction is often expressed as a product of load and constant to the given fractional power.

F = KLn

•Rolling friction force is inversely proportional to the radius of curvature and is directly proportional to load.

F = μ×W/r

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Causes of Rolling Friction

When given objects or substances are rolled onto a surface, certain things happen:

1.The object is usually deformed at the point of contact with the present surface.

2.The surface is usually deformed at the point of contact with the present object.

3.The motion is often created below the surface as a result of the above-mentioned two points.

The primary and main cause of this rolling friction is that the energy of deformation is usually greater than that of energy of recovery. Also, there is an adhesive force present between the two surfaces which needs to be overcome constantly.

The amount of friction is usually based on some variety of factors such as:

1.The sliding body (object) quality

2.The surface Load quality

3.The rolling object diameter

4.The body (object) surface area

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Coefficient of Rolling Friction

Determination of the coefficient of this friction is usually more complex than that of sliding friction.

“Coefficient of Rolling Friction is the given ratio of the force of rolling friction to the total weight of that object.”

The coefficient of rolling resistance in empirical terms can be expressed as:

Fr = μr W

where,

Fr →resistive force of rolling resistance

μr →coefficient of rolling resistance

W →weight of the rolling body

Rolling Friction Examples

•A basketball that is rolled on the court will obviously come to a halt due to its rolling friction.

•A bike which has broad tires will eventually burn more fuel as compared to others because of the increased rolling friction.

•A ball that is rolled on a field will go at a very lesser distance than that of a ball rolling on a concrete floor because it will eventually experience greater rolling friction on the former surface.

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