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Friction is a force that opposes the motion of two surfaces in contact. It occurs when the surfaces rub against each other, generating heat and wearing down the surfaces.
The amount of friction between two bodies is affected by the type of surfaces, the force pressing the surfaces together, and the smoothness of the surfaces.
Friction between two bodies can be measured using a device called a friction meter, which measures the force required to move one surface over another.
There are three types of friction: static friction, which prevents motion between two surfaces; kinetic friction, which occurs when two surfaces are in motion; and rolling friction, which is the resistance to motion when an object rolls over a surface.
Friction can be reduced by using lubricants between two surfaces, smoothing or polishing the surfaces, or using wheels or rollers. It can be increased by increasing the force between the surfaces, using rough or sticky surfaces, or increasing the contact area between the surfaces.