# Rolling Friction

## Rolling Friction

Whenever the surface of an object slides over another, each object experiences a contact force. Which always opposes the relative motion between the surfaces, this contact force is called as frictional force. This force acts tangentially to the interface of two bodies.

What is Rolling Friction?

For a moving solid body, there are two principal types of friction that act upon it:

Rolling Friction: The force resisting the motion of a rolling object on a surface is known as Rolling Friction or Rolling Resistance. This type of friction s experience by a wheel or a ball rolling on the ground. Force of friction which comes into play, between two surfaces, while one is rolling over the other is called rolling friction.  Rolling friction is similar to kinetic friction. So,

fr = μr N.

Where,

μr = Co – efficient of Rolling Friction,

N = Normal Force.

Sliding Friction: Which resists the movement of a body which is pushed in such a way that only one surface of the body is in contact with the surface it is moving on. It will be experienced when an object is pushed across a table.

Cause of Rolling Friction: When a body is rolled on a surface, the body is deformed at the point of contact with the surface and the surface is deformed at the point of contact with the object.

The major cause of friction is the energy of deformation is greater than the energy of recovery, also there is an adhesive force between the two surfaces. The amount of friction is based on the quality of the sliding body, quality of the surface, load and diameter of the rolling object etc.

Daily life Examples of Rolling Friction:

• A bike with a broad tire will burn more fuel because of the increased rolling friction.
• A car will eventually come to a stop if just allowed to roll as the friction between the road surface and the wheels causes friction that causes the vehicle to stop.
• A soccer ball kicked across a grassy field will slow more quickly than one kicked across a smooth, hard surface because the rolling friction is far greater on the field.
• A skateboard set on a slight decline will eventually stop itself because of the resistance caused by the friction between the wheels and the surface.

As you can see, many daily life objects use rolling friction. There are examples everywhere in the world.