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# Rolling Friction

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 Sub Topics The concept of rolling friction leads to the invention of wheel, which is a well known findings in human history. Locomotion mechanism is the best illustration for the rolling friction. A wheel is an efficient mechanism for explaining locomotion on the hard surfaces which is common in nature. This motion tells that the rolling friction is connected to deformation than the sliding friction. If we compare the rolling and sliding friction, we can see that the energy loss of rolling friction is lesser compared to that of sliding friction. Even though the energy loss is less it is very important in technological field due to the applications. For example, in automobiles the energy loss due to the rolling friction between the tires and the road.

## What is Rolling Friction?

When we are discussing about the friction, the main types comes under the friction is static, kinetic and rolling friction. Static friction acting on a rolling body can be in two directions. One is in the direction of motion and other is opposite to the motion, it depends on the force acting on this rolling body. Generally, the direction of rolling friction is not mentioned. When a spherical body rolls on the horizontal surface with out any push or pull, the rotational and translational velocities are decreases. This is due to the rolling friction of the body. It does not helps to finding the direction of the motion, hence it is known as rolling friction.

## Rolling Friction Definition

Rolling friction is the frictional force which opposes or resists the motion of an object which is rolling through a surface. Rolling friction is also known as rolling resistance or rolling drag.

## Rolling Friction Formula

The equation for finding the rolling friction is given by,

$F_{r}$ = CW
Where $F_{r}$ is the rolling friction
C is the rolling friction coefficient
W is the force or weight of a body

## Coefficient of Rolling Friction

Coefficient of rolling friction is denoted as C and is defined as the force required to push a spherical body per unit force of weight. The formula is given by,

C = $\frac{F_{r}}{W}$

The value of the coefficient of friction of some materials are listed below.

 Tread Material Floor Material Coefficient of Rolling Friction Forged Steel Steel 0.019 Cast Iron Steel 0.021 Hard Rubber Steel 0.303 Polyurethane Steel 0.030-0.057 Cast Nylon Steel 0.027 Phenolic Steel 0.026 Ordinary car tire Road 0.015 Truck tire Road 0.006-0.01 Train Wheel Track 0.001

## Rolling Without Slipping Friction

Rolling without slipping generally occurs when a spherical body such as a wheel, cylinder, or ball rolls on a surface without skidding.

In rolling with out slipping, the below things will happen:
• If a body rolls without slipping, the bottom of the rolling body must be momentarily at rest relative to a constant observer.
• In this type friction, the motion of a center of mass and the rotational motion about its center of mass comes in to picture.
• In this case, distance, velocity and the acceleration of the center of mass of a rolling body is directly related to the angle of rotation, the angular velocity and the angular acceleration about the center of mass of a body.