Friction is the force that opposes the relative motion or tendency of such motion of two surfaces in contact. It is not, however, a fundamental force, as it originates from the electromagnetic forces and exchange force between atoms. In situations where the surfaces in contact are moving relative to each other, the friction between the two objects converts kinetic energy into heat (atomic vibrations). Friction between solid objects and fluids (gases or liquids) is called fluid friction. See also aerodynamics and hydrodynamics.
Friction is an extremely important force - it propels automobiles and other ground transport and holds nails, screws and nuts, along with many other uses.

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KoreaBeral Co., Ltd. - Makes brake pads and shoes. Factories in Asan and Daegu. [Korean, English, Japanese, Chinese]
Sangshin Brake Ind. Co., Ltd. - Maker of brake linings and pads. [Korean, English]
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