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

Edited By Vishal kumar | Updated on Jul 02, 2025 04:35 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 do not slide on the floor. However, the wheels roll on the floor.

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

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 in relation to the floor remains zero, and hence, the wheel keeps moving forward.

What is Rolling Friction?

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

The rolling of a football, tennis ball, or even a wheel on the ground is an example of Rolling friction.

What is Sliding Friction?

In this type of friction, there are restrictions on the 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 for 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 in the rotating parts of the wheel machines that are known as the ball bearings.

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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. $\mathrm{F}=\mathrm{KLn}$
Rolling friction force is inversely proportional to the radius of curvature and is directly proportional to load. $F=\mu \times W / r$

Causes of Rolling Friction

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

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

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

The primary cause of this rolling friction is that the energy of deformation is usually greater than that of recovery energy. Also, an adhesive force exists between the two surfaces that need to be constantly overcome.

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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:

$$
\mathrm{Fr}=\mu \mathrm{r} \mathrm{~W}
$$

where,

$\mathrm{Fr} \rightarrow$ resistive force of rolling resistance
$\mu \mathrm{r} \rightarrow$ coefficient of rolling resistance
$\mathrm{W} \rightarrow$ weight of the rolling body

Factors Affecting Rolling Friction

Following are some of the factors affecting rolling friction:

The shape of the given wheel or the given curved surface
Nature of the given surface on which the object is rolling
Wheel speed
Wheel radius
The nature of the wheel material or even the curved surface

Examples of Rolling Friction

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

Difference between Rolling Friction and Sliding Friction

Aspects	Rolling Friction	Sliding Friction
Definition	Resistance is when an object rolls over a surface.	Resistance is when an object slides over a surface.
Motion Type	Rolling motion (e.g., wheels, balls).	Sliding motion (e.g., dragging a box).
Friction Force	Lower than sliding friction.	Higher than rolling friction.
Surface Interaction	Less surface area in contact.	More surface area in contact.
Example	A car tire rolling on the road.	Pushing a heavy box across the floor.
Ease of Movement	Easier to move due to less resistance.	Harder to move due to more resistance.

Frequently Asked Questions (FAQs)

1. What is the coefficient of rolling resistance?

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

Fr = μr W

2. What are the two types of friction?

The two types of friction are…

Rolling friction

Sliding friction

3. What is the example of sliding friction?

Pulling or pushing a box is an example of sliding friction.

4. What is the example of rolling friction?

Rolling a ball in circular motion on the ground is an example of rolling friction.

5. In what areas does rolling friction depend?

•The shape of the wheel or curved area.

•The nature of the rolling area.

•Wheel speed.

•Type of tire material or curved area.

6. What causes rolling friction?

Rolling friction is caused by several factors: deformation of the rolling object and/or the surface, adhesion between the surfaces, and microscopic roughness of the surfaces. The main contributor is usually the deformation of materials.

7. How does rolling friction differ from sliding friction?

Rolling friction is typically much less than sliding friction because the object (like a wheel) rotates instead of sliding across the surface. This reduces the area of contact and the amount of deformation, resulting in less resistance to motion.

8. Can rolling friction ever be zero?

In reality, rolling friction can never be exactly zero due to the inevitable deformation of materials and microscopic imperfections in surfaces. However, it can be minimized to very small values in certain conditions.

9. What is the coefficient of rolling friction?

The coefficient of rolling friction is a dimensionless number that represents the ratio of the force of rolling friction to the normal force between the rolling object and the surface. It's typically much smaller than the coefficient of sliding friction.

10. How is the coefficient of rolling friction typically expressed?

The coefficient of rolling friction is often expressed as a ratio of the radius of the rolling object to the distance the center of mass is displaced due to deformation. It's usually denoted by μr or Crr.

11. Can rolling friction ever help motion?

While rolling friction typically opposes motion, it can sometimes aid it. For example, the rolling friction between a car's tires and the road allows the car to move forward by providing traction. Without this friction, the wheels would spin in place.

12. How does rolling friction affect the motion of a ball rolling down an inclined plane?

Rolling friction slows down a ball rolling down an inclined plane. It reduces the ball's acceleration and final velocity compared to what would be expected in an ideal, frictionless scenario.

13. Why do wider tires generally have more rolling friction?

Wider tires typically have more rolling friction because they have a larger contact patch with the ground. This increased area of contact leads to more deformation and thus more energy loss, resulting in greater rolling friction.

14. Why is rolling friction important in vehicle design?

Rolling friction is crucial in vehicle design because it directly affects fuel efficiency. Lower rolling friction means less energy is wasted overcoming resistance, leading to better fuel economy and reduced emissions.

15. How does the hardness of materials affect rolling friction?

Generally, harder materials experience less rolling friction because they deform less under pressure. For example, a steel ball bearing will typically have less rolling friction than a rubber ball of the same size and weight.

16. What is rolling friction?

Rolling friction is the force that resists the motion of a rolling object, such as a wheel or ball, as it moves along a surface. It's generally much less than sliding friction, which is why wheels are used to make movement easier.

17. What's the difference between static and kinetic rolling friction?

Static rolling friction is the force needed to start an object rolling from rest, while kinetic rolling friction is the force that continues to oppose the motion once the object is rolling. Static rolling friction is typically slightly higher than kinetic rolling friction.

18. What's the relationship between rolling friction and energy loss?

Rolling friction leads to energy loss as it converts kinetic energy into heat through deformation and other processes. This is why a rolling object will eventually come to a stop on a level surface if no additional force is applied.

19. What's the relationship between rolling friction and the concept of rolling without slipping?

For an object to roll without slipping, there must be enough friction to prevent sliding. This friction, while necessary for pure rolling, also contributes to rolling friction. The ideal amount allows for rolling without excessive energy loss.

20. What role does rolling friction play in the concept of mechanical advantage?

Rolling friction is an important consideration in mechanical advantage. While using wheels or rollers can greatly reduce friction compared to sliding, the remaining rolling friction still needs to be overcome. This affects the efficiency and required input force in mechanical systems.

21. How does the concept of moment of inertia relate to rolling friction?

Moment of inertia affects how easily an object can start or stop rolling. Objects with higher moments of inertia require more force to start rolling (overcoming static rolling friction) and to stop rolling. This is related to, but distinct from, the force needed to overcome rolling friction during constant motion.

22. What's the relationship between rolling friction and the concept of self-aligning bearings?

Self-aligning bearings are designed to minimize the effects of misalignment, which can increase rolling friction. By allowing some degree of rotation or tilting, these bearings ensure that the rolling elements maintain optimal contact, reducing friction and wear even when the shaft and housing are not perfectly aligned.

23. What factors affect the magnitude of rolling friction?

The magnitude of rolling friction is affected by the materials of the rolling object and surface, their smoothness, the weight of the rolling object, its speed, temperature, and the presence of any lubricants or contaminants.

24. How does the weight of a rolling object affect rolling friction?

Increasing the weight of a rolling object generally increases rolling friction. This is because more weight leads to greater deformation of both the object and the surface, resulting in more energy loss during rolling.

25. How does rolling friction affect the efficiency of machines?

Rolling friction can significantly impact machine efficiency. While it's generally less than sliding friction, it still represents energy loss. Engineers often use ball bearings or other rolling elements to reduce friction and improve efficiency in rotating machinery.

26. Why do bicycle racers use narrow, high-pressure tires?

Bicycle racers use narrow, high-pressure tires to minimize rolling friction. The narrow profile reduces the contact patch with the road, while high pressure minimizes tire deformation. Both factors contribute to lower rolling friction and thus higher speed.

27. How does rolling friction compare on different surfaces?

Rolling friction varies depending on the surface. Hard, smooth surfaces like concrete generally have less rolling friction than soft or rough surfaces like sand or gravel. This is due to differences in deformation and surface interactions.

28. Can rolling friction be beneficial in any situations?

Yes, rolling friction can be beneficial in many situations. It provides necessary traction for vehicles to move and turn, allows for controlled descent on inclines, and enables the functioning of many mechanical systems that rely on wheels or rollers.

29. How does the diameter of a wheel affect rolling friction?

Generally, larger diameter wheels experience less rolling friction. This is because they have a smaller angle of contact with the surface, leading to less deformation and thus less energy loss. This is one reason why bicycle wheels are relatively large.

30. How does rolling friction affect the stopping distance of a vehicle?

Rolling friction helps to slow down a vehicle, but its effect is relatively small compared to braking friction. However, it does contribute to the overall stopping distance, especially at higher speeds where rolling friction increases.

31. Why do some surfaces, like rubber, seem to have more rolling friction?

Materials like rubber tend to have more rolling friction because they deform more easily. This increased deformation leads to more energy loss as the object rolls, resulting in higher rolling friction compared to harder materials.

32. How does rolling friction change with speed?

Generally, rolling friction increases with speed. This is partly due to increased deformation at higher speeds and partly due to air resistance, which becomes more significant as speed increases.

33. How does temperature affect rolling friction?

Temperature can affect rolling friction by changing the properties of the materials involved. For example, rubber tires may become softer and experience more deformation (and thus more rolling friction) at higher temperatures.

34. Why is rolling friction important in the design of conveyor belts?

Rolling friction is crucial in conveyor belt design because it affects the power required to operate the system. Lower rolling friction means less energy is needed to keep the belt moving, improving efficiency and reducing operating costs.

35. How does lubrication affect rolling friction?

Lubrication can reduce rolling friction by minimizing direct contact between surfaces and reducing adhesion. However, its effect is generally less dramatic than in sliding friction because rolling already involves less surface contact.

36. How does the shape of a rolling object affect rolling friction?

The shape of a rolling object significantly affects rolling friction. Spheres and cylinders generally have less rolling friction than more complex shapes because they maintain a consistent, small contact area with the surface as they roll.

37. Why do train wheels have a conical shape?

Train wheels have a conical shape to reduce rolling friction and wear, especially when turning. The shape allows the wheel to naturally adjust its effective diameter when going around curves, reducing slippage and associated friction.

38. How does rolling friction affect the motion of a pendulum?

In a real pendulum, rolling friction at the pivot point causes the amplitude of oscillations to decrease over time. This is why pendulums eventually come to rest instead of swinging forever as they would in an ideal, frictionless scenario.

39. What's the difference between rolling friction and rolling resistance?

While often used interchangeably, rolling resistance is a broader term that includes all forces resisting the motion of a rolling object, including rolling friction, air resistance, and internal friction in the rolling mechanism. Rolling friction specifically refers to the friction between the rolling object and the surface.

40. How does rolling friction affect the design of ball bearings?

Ball bearings are designed to minimize rolling friction. They use hard, smooth materials and precise manufacturing to reduce deformation and surface irregularities. The size and number of balls are optimized to distribute load and minimize overall friction.

41. Can rolling friction ever increase with use?

Yes, rolling friction can increase with use due to wear and tear. As surfaces become rougher or materials deform permanently, rolling friction may increase. This is why regular maintenance and replacement of rolling components (like bearings or wheels) is important in many machines.

42. Why do some vehicles use different tire widths on front and rear axles?

Different tire widths can be used to balance performance characteristics. Wider tires may provide better traction but have more rolling friction. By using different widths, designers can optimize factors like steering response, traction, and overall rolling resistance for the vehicle's intended use.

43. How does rolling friction affect energy conservation in physics problems?

In many introductory physics problems, rolling friction is often neglected to simplify calculations. However, in real-world scenarios, rolling friction causes energy to be dissipated as heat, meaning that mechanical energy is not conserved. Accounting for this can be important in more advanced or applied problems.

44. What's the relationship between rolling friction and the coefficient of restitution?

While not directly related, both rolling friction and the coefficient of restitution affect the behavior of rolling objects. Rolling friction determines how quickly a rolling object will slow down, while the coefficient of restitution determines how much energy is conserved when the object bounces or collides.

45. How does rolling friction affect the design of wind turbines?

In wind turbines, minimizing rolling friction in the bearings is crucial for efficiency. Lower friction means more of the wind's energy can be converted to electrical energy. However, the bearings must also be designed to handle the large forces involved, which can increase friction.

46. Why is understanding rolling friction important in robotics?

Understanding rolling friction is crucial in robotics for accurate motion control and energy efficiency. It affects the power required for movement, the precision of positioning, and the overall performance of wheeled or rolling robotic systems.

47. How does rolling friction relate to the concept of mechanical impedance?

Rolling friction contributes to the mechanical impedance of a rolling system. It represents a form of energy dissipation that opposes motion, affecting how the system responds to applied forces or torques. Understanding this relationship is important in designing and analyzing dynamic mechanical systems.

48. Can rolling friction ever be negative?

In classical physics, rolling friction is always a resistive force and cannot be negative. However, in certain specialized scenarios (like some types of bearings under specific conditions), the overall rolling resistance might appear negative due to other factors, though this is not true negative friction.

49. How does rolling friction affect the design of planetary rovers?

For planetary rovers, understanding rolling friction is crucial for navigation and energy management. The unique surfaces of other planets (like Mars) present challenges in terms of rolling friction, affecting wheel design, power requirements, and overall mission planning.

50. What role does rolling friction play in the physics of curling (the sport)?

In curling, rolling friction between the stone and the ice is minimized by a thin water layer created by the stone's motion. Understanding and manipulating this low-friction interaction is key to the strategy of the game, as it allows for the stone's characteristic curved path.

51. How does rolling friction affect the motion of a yo-yo?

Rolling friction at the axle of a yo-yo affects its spin time and behavior. While some friction is necessary for the yo-yo to "sleep" (spin at the end of its string), too much friction will cause it to slow down and return too quickly. Competitive yo-yos often use high-quality bearings to minimize unwanted friction.

52. How does rolling friction affect the design of conveyor rollers in industrial settings?

In industrial conveyor systems, minimizing rolling friction in the rollers is crucial for energy efficiency and longevity. Designers must balance factors like roller material, bearing type, and surface finish to reduce friction while maintaining durability under heavy loads and continuous operation.

53. What role does rolling friction play in the physics of bowling?

In bowling, rolling friction between the ball and the lane affects the ball's speed and trajectory. The oil pattern on the lane is designed to manipulate this friction, creating areas of higher and lower friction that skilled bowlers can use to control the ball's path.

54. How does the concept of rolling friction apply to non-circular objects, like a polygon "rolling" down an incline?

For non-circular objects like polygons, the motion is not smooth rolling but a series of rotations and impacts. Each impact causes energy loss similar to rolling friction. The "effective" rolling friction for such objects is generally much higher than for circular objects, explaining why they come to rest more quickly on an incline.

55. How might rolling friction be different in microgravity environments, such as on the International Space Station?

In microgravity, the normal force between rolling objects and surfaces is greatly reduced, which in turn reduces rolling friction. However, other factors like adhesion between surfaces might become more significant. Understanding these differences is important for designing mechanisms that need to roll or rotate in space environments.