The term rolling friction refers to the resistance created by an object rolling across a surface. Synonymous terms include rolling drag and rolling resistance. Learn more about what rolling friction is and get several rolling friction examples.
Understanding Rolling Friction
When you roll a ball down the road, it doesn't roll forever. Why? Because of rolling friction. This force will hold back the ball from rolling forever and eventually make it stop. In technical speak, the rolling friction definition is "the force that opposes motion when a round object rolls over another surface." Essentially, it's the force that slows down a wheel or ball in motion.
Frictional Force Equation
The amount of friction created by a rolling object is less than the friction created by normal force. It is dramatically less than other types of friction, such as sliding friction. The actual rolling friction can be measured and expressed as a number multiplied by the normal force or using the equation: (Fr = μrN).
Objects With Rolling Friction
Any ball or wheel has rolling friction when rolled on a surface. Some examples of items that have rolling friction include:
- truck tires
- ball bearings
- bike wheels
- a soccer ball, basketball or baseball
- car tires
- skateboard tires
- railroad steel wheels
- a bowling ball
- a ping pong ball
- a bouncy ball
- roller skate wheels
Everyday Examples of Rolling Friction
Sometimes rolling friction can be a hard concept to understand. Therefore, you can look at different examples of rolling friction to help you out.
- A car will eventually stop if just allowed to roll, as the friction between the road surface and the wheels causes the vehicle to stop.
- Thicker bike wheels will lessen the potential speed of the bike because there is a greater wheel surface to create friction against the road or path, which will slow the bike.
- Heavy-duty trucks get greater gas mileage when tread begins to wear on the tires because there is less rolling friction, allowing the truck to move more quickly with less resistance.
- 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.
- 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.
- When a train goes around a curve there is greater rolling friction.
- Roller skates have greater rolling friction than rollerblades because there is more surface-to-wheel contact on roller skates.
- A duckpin bowling ball is likely to have less rolling friction than a full-sized bowling ball because of its size and weight, which create less rolling friction.
- A dump truck will have greater rolling friction than a small car because the dump truck is a heavier load bearing down on the wheel, causing greater rolling friction.
Factors That Affect Rolling Friction
There are factors that can create more or less rolling friction. For example, the shape of a wheel can make more or less rolling friction. Explore these factors that affect rolling friction on an object.
- type of surface on which the wheel is rolling
- any movement of the surface or below the surface
- original speed of the wheel
- diameter of the wheel
- amount of pressure on the wheel
- adhesion of the surface
- any amount of sliding that occurs in addition to the rolling motion
- deformation of an object or the surface
- overinflation of tires
- the thickness of tread on tires
- the shape of tread on tires
- the material that the wheel or ball is made of
Knowing Your Rolling Friction
As you can see, many everyday objects use rolling friction. There are examples everywhere in the world. Want to know more about friction? Explore the 4 types of friction out there.