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Kasturi Talukdar

Updated on 06th October, 2023 , 6 min read

Rolling Friction: Definition, Examples, Laws, Causes, Coefficient and Formula

What is Rolling Friction Overview

Rolling friction, also known as rolling resistance, is a type of frictional force that occurs when one object rolls over another. It is an essential concept in physics and engineering, playing a crucial role in various fields such as transportation, mechanics, and everyday life. Understanding rolling friction is key to optimizing the design and performance of vehicles, machines, and even sports equipment. This article will provide a detailed explanation of rolling friction, including its definition, causes, and examples.

What is Rolling Friction?

The force that opposes the motion of a rolling body is referred to as rolling friction. When a ball is rolling on the ground, it ultimately comes to a stop. This is due to the ball encountering resistance in the direction of its velocity, meaning that a force is opposing the ball's motion and reducing its speed. Rolling friction is the name for this opposing force. The deformation of surfaces is the primary contributor to rolling friction. For instance, bowling balls, car tires, and ball bearings all experience rolling friction.

rolling friction

Advantages and Disadvantages of Rolling Friction

Advantages of Rolling Friction

Disadvantages of Rolling Friction

It minimizes the effort involved in moving objects. For example, stroller bags and conveyor belts make it easier to move heavy objects.  When rolling friction comes into play, speed becomes an obvious factor. But there will be limitations in controlling and maneuvering capabilities. That is why it's much easier to move around in shoes than on roller skates.
For a comfortable ride in vehicles, rolling friction is important or else if the wheels of vehicles would have been based on sliding friction the ride would be very tiresome and uncomfortable.It is challenging to walk on surfaces with rolling objects because rolling friction is less than sliding friction.
Due to rolling friction, it becomes easier for us to move faster using roller skates than on shoes. Rolling friction results in the dissipation of energy in the form of heat. When an object rolls, there is a continuous conversion of kinetic energy into heat energy due to the interaction between the rolling object and the surface. This energy loss can reduce the overall efficiency of a system or device.

Formula for Calculating Rolling Friction

There are two formulas for rolling friction that are derived from the laws of rolling friction. These include:

F = KLn

Here, 

F= rolling friction

K = load

L = constant to fractional power.

F= μ×W/r

Here, 

F= force of rolling friction

μ = coefficient of rolling friction

W= load (weight/mass)

r = radius of curvature.

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Laws of Rolling Friction

As we previously discussed, rolling friction is based on three principles of motion, which are as follows:

  • The amount of rolling friction decreases as smoothness increases.
  • Rolling friction is a fractional power product of load and constant.
  • The force of rolling friction is inversely proportional to the radius of curvature and directly proportional to the load.
  • Rolling friction can be expressed as a fractional power of the product of the load and the constant: F = kLn 
  • Rolling friction force is inversely proportional to curvature radius and directly proportional to load: F = μ×W/r

rolling friction

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What is Rolling Friction Cause

When an item rolls on the surface, certain things happen. As follows:

  1. The item gets distorted when it comes into contact with the surface.
  2. The item's surface deforms when it comes into contact with it.
  3. The motion is created under the surface because of the concepts explained above.
  4. The deformation energy is greater than the recovery energy, which is the primary cause of this friction. Additionally, there is a constant adhesive force acting between the two surfaces. 

rolling friction

The amount of friction is influenced by these factors, including:

  • The quality of the sliding body 
  • The surface's quality Load
  • The diameter of the rolling object
  • Area of the body's surface

What is Rolling Friction 

Although determining the coefficient of rolling friction is more difficult than determining the coefficient of sliding friction, the following statement and formula can help.

"The rolling friction coefficient is defined as the ratio of the rolling friction force to the total weight of the object."

Formula:

Fr =μrW 

Where, 

Frstands for the rolling resistance's resistive force.

μrstands for the rolling resistance coefficient.

Wis the weight of the moving body.

Solved Examples of Rolling Friction Coefficient

Example: A cart with a mass of 50 kg is rolling on a flat surface. The force required to keep the cart rolling at a constant speed is measured at 25 N. Calculate the coefficient of rolling friction.

Solution:

To calculate the coefficient of rolling friction, we can use the formula:

F = μ × W

where F is the force of rolling friction, μ is the coefficient of rolling friction, and W is the weight or load.

In this example, the force of rolling friction (F) is given as 25 N, and the weight (W) can be calculated by multiplying the mass (m) by the acceleration due to gravity (g), which is approximately 9.8 m/s^2.

W = m × g

W = 50 kg × 9.8 m/s^2

W = 490 N

Substituting the known values into the formula:

25 N = μ × 490 N

To isolate μ, we can divide both sides of the equation by 490 N:

25 N / 490 N = μ

0.051 = μ

Therefore, the coefficient of rolling friction (μ) in this example is approximately 0.051.

 

Rolling Friction Examples

Here are some examples of rolling friction in short and crisp points:

  1. Vehicle Tires on Roads: Rolling friction between vehicle tires and the road surface provides traction for acceleration, deceleration, and turning.
  2. Ball Sports: Rolling friction is essential in sports like soccer, basketball, and bowling, where the ball rolls on the playing surface.
  3. Bearings: Rolling friction is utilized in bearings, such as those in wheels, rollers, and conveyor systems, to enable smooth rotation with reduced friction.
  4. Skateboarding and Rollerblading: Rolling friction allows skateboard and rollerblade wheels to roll smoothly on the ground, enabling movement.
  5. Bicycle and Motorcycle Tires: Rolling friction between tires and the road allows bicycles and motorcycles to move forward efficiently.
  6. Luggage Wheels: Rolling friction enables luggage wheels to roll smoothly, making it easier to transport heavy bags.
  7. Automotive Industry: Rolling friction affects fuel efficiency and tire wear in vehicles, prompting the development of low rolling resistance tires.
  8. Industrial Equipment: Rolling friction is present in machinery and equipment with rotating parts, such as gears, pulleys, and conveyors.
  9. Caster Wheels: Rolling friction in caster wheels allows easy movement of furniture, carts, and other objects.
  10. Exercise Equipment: Rolling friction is involved in the movement of treadmills, elliptical trainers, and stationary bicycles.

Difference Between Rolling and Sliding Friction

The difference between sliding and rolling friction is that sliding friction happens when two surfaces rub against one another, whereas rolling friction happens when an object rolls on a surface.

Rolling Friction:

  1. Rolling friction occurs when an object rolls on a surface.
  2. It is caused by the deformation of surfaces and the interlocking between the rolling object and the surface.
  3. The coefficient of rolling friction (μr) depends on factors such as the radius of the rolling object, the depth of deformation, and the surface characteristics.
  4. The formula for calculating rolling friction is: Fr= μrN, where Fr is the rolling friction force, μr is the coefficient of rolling friction, and N is the normal force exerted on the object.

Sliding Friction:

  1. Sliding friction occurs when two surfaces slide or rub against each other.
  2. It is caused by the interlocking and interactions between the microscopic roughness of the surfaces.
  3. The coefficient of sliding friction (μs) varies depending on factors such as surface roughness and temperature. It is generally considered an external property and is independent of the applied load.
  4. The formula for calculating sliding friction is: Fk= μrN, where Fk is the sliding friction force, μs is the coefficient of sliding friction, and N is the normal force exerted between the surfaces.

What is Rolling Friction: Things to Remember

  1. To slow down and eventually stop an object from rolling across a surface, rolling friction is the resistive force that any surface offers to oppose the object's rolling motion.
  2. Increased smoothness results in a decrease in rolling friction force.
  3. The load and curvature radius have opposite relationships for rolling friction force, which is directly proportional to load.
  4. At the point of contact, the object and surface are both altered.
  5. Since the friction on the former surface will be greater, a ball rolling on a field will travel less than a ball on a concrete floor.

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Frequently Asked Questions

What is rolling friction?

Rolling friction is the force that opposes the motion of a rolling object. It is much less than sliding friction for the same pair of objects. When one object rolls upon another, there is theoretically no sliding or slip between them.

What are some examples of rolling friction?

Some examples of rolling friction include: 1. A ball rolling on the ground 2. A car driving on a road 3. A wheelbarrow rolling down a hill 4. A train rolling on its tracks

What are the causes of rolling friction?

The main cause of rolling friction is the deformation of the objects in contact. When an object rolls, it deforms the surface it is rolling on. This deformation creates a force that opposes the motion of the object.

How can rolling friction be reduced?

Rolling friction can be reduced by: 1. Using smooth surfaces 2. Reducing the weight of the objects in contact 3. Using lubricants

What is the difference between rolling friction and sliding friction?

Sliding friction is the force that opposes the motion of two objects that are sliding against each other. Rolling friction is the force that opposes the motion of an object that is rolling on another object. Rolling friction is always less than sliding friction for the same pair of objects.

What are the effects of rolling friction?

Rolling friction can have a number of effects, including: Increasing the energy required to move an object, Reducing the efficiency of machines, Increasing the wear and tear on objects.

What are some of the applications of rolling friction?

Some of the applications of rolling friction include: Transportation, Manufacturing, Construction, Sports etc.

What are some of the challenges associated with rolling friction?

Some of the challenges associated with rolling friction include: 1. It can be difficult to predict the amount of rolling friction that will occur 2. Rolling friction can vary depending on the materials in contact 3. Rolling friction can increase with the weight of the objects in contact

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