Rolling Friction - Definition, Examples, Coefficient, Causes, FAQs
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.
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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Download E-bookCoefficient 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)
Q: What is the coefficient of rolling resistance?
A:
The coefficient of rolling resistance in empirical terms can be expressed as:
Fr = μr W
Q: What are the two types of friction?
A:
The two types of friction are…
Rolling friction
Sliding friction
Q: What is the example of sliding friction?
A:
Pulling or pushing a box is an example of sliding friction.
Q: What is the example of rolling friction?
A:
Rolling a ball in circular motion on the ground is an example of rolling friction.
Q: In what areas does rolling friction depend?
A:
•The shape of the wheel or curved area.
•The nature of the rolling area.
•Wheel speed.
•Type of tire material or curved area.
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