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# What are some examples of rolling friction?

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Examples of rolling friction are a roller skate slowing down on pavement or the wooden surface of a roller-skate rink and a basketball rolling across the surface of the court. When one surface rolls across another, small indentations on both surfaces interfere with each other, reducing speed.

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Friction is a requirement for the beginning, ending and alteration of the movement of a wheel or other rolling object. When a car spins its tires against the road, friction is necessary to stop the slippage and allow the tires to get purchase on the ground and begin their rolling motion. As the tires move, though, the interaction between the indentations on the tire and the indentations on the ground builds a torque that slows the angular velocity of the tire.

As the rolling motion takes place, the shape of both objects change as well. For example, the wheel flattens slightly, while the surface develops a trench that holds the entire flattened edge of the wheel. The force of the friction spreads throughout the whole area at which the surfaces come into contact with one another. The front of the wheel also shrinks a bit in response to making a type of plowing motion along the surface.

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## Related Questions

• A:

Friction can be reduced by adding a lubricant or by smoothing and polishing surfaces, according to the HyperPhysics program at Georgia State University. For some substances, smoothing only reduces friction to a point, after which friction increases with further smoothing.

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• A:

The main source of attraction between two metals, or adhesion, is what causes friction, and any increase of friction requires an increase in adhesion. Friction itself is the force of resistance against two objects as one object slides or rolls over another. This force increases the amount of energy required to move an object a set distance.

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• A:

Friction can be increased by increasing the surface roughness of the objects that are in contact while friction can be decreased by smoothing out the objects or stopping the objects if moving. There are two primary types of friction used in science: static friction and kinetic friction.