Friction

Topics: Friction, Force, Classical mechanics Pages: 4 (1091 words) Published: December 5, 2014
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Friction
Definition: Friction is the force resisting the relative lateral (tangential) motion of solid surfaces, fluid layers, or material elements in contact. Force of friction:-
Friction is a force that is created whenever two surfaces move or try to move across each other. • Friction always opposes the motion or attempted motion of one surface across another surface. • Friction is dependant on the texture of both surfaces.

• Friction is also dependant on the amount of contact force pushing the two surfaces together (normal force). Factors affecting friction:-
Friction depends partly on the smoothness of the contacting surfaces, a greater force being needed to move two surfaces past one another if they are rough than if they are smooth. However, friction decreases with smoothness only to a degree; friction actually increases between two extremely smooth surfaces because of increased attractive electrostatic forces between their atoms. Friction does not depend on the amount of surface area in contact between the moving bodies or (within certain limits) on the relative speed of the bodies. It does, however, depend on the magnitude of the forces holding the bodies together. When a body is moving over a horizontal surface, it presses down against the surface with a force equal to its weight, i.e., to the pull of gravity upon it; an increase in the weight of the body causes an increase in the amount of resistance offered to the relative motion of the surfaces in contact. Methods of reducing frictions:-

Devices: Devices such as wheels, ball bearings, air cushion or roller bearing can change sliding friction into a much smaller type of rolling friction. Many thermoplastic materials such as nylon, HDPE and PTFE are commonly used for low friction bearings. They are especially useful because the coefficient of friction falls with increasing imposed load. Lubricants: A common way to reduce friction is by using a lubricant, such as oil, water, or...