![]() Note, however, unlike the other systems the force unit is not equal to the mass unit multiplied by the acceleration unit -the use of Newton's second law, F = m ⋅ a, requires another factor, g c, usually taken to be 32.174049 (lb⋅ft)/(lbf⋅s 2). This is convenient because one pound mass exerts one pound force due to gravity. ![]() In the "engineering" systems (middle column), the weight of the mass unit (pound-mass) on Earth's surface is approximately equal to the force unit (pound-force). The standard values of acceleration of the standard gravitational field ( g n) and the international avoirdupois pound (lb) result in a pound-force equal toĤ.4482216152605 N. ![]() The pound-force is the product of one avoirdupois pound ( exactly 0.45359237 kg) and the standard acceleration due to gravity, 9.80665 m/s 2 (32.174049 ft/s 2). Product of avoirdupois pound and standard gravity The 20th century, however, brought the need for a more precise definition, requiring a standardized value for acceleration due to gravity. Since the 18th century, the unit has been used in low-precision measurements, for which small changes in Earth's gravity (which varies from equator to pole by up to half a percent) can safely be neglected. The pound-force is equal to the gravitational force exerted on a mass of one avoirdupois pound on the surface of Earth. Pound-force should not be confused with pound-mass (lb), often simply called "pound", which is a unit of mass nor should these be confused with foot-pound (ft⋅lbf), a unit of energy, or pound-foot (lbf⋅ft), a unit of torque. The pound of force or pound-force (symbol: lbf, sometimes lb f, ) is a unit of force used in some systems of measurement, including English Engineering units and the foot–pound–second system. Pound-forceĮnglish Engineering units, British Gravitational System ![]() For other uses, see Pound (disambiguation). ![]()
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