Pound-force
From Free net encyclopedia
The pound-force is a non-SI unit of force or weight (properly abbreviated "lbf" or "lbf"). The pound-force is equal to a mass of one avoirdupois pound (which is currently defined as exactly 0.45359237 kilogram) multiplied by the standard acceleration due to gravity on Earth. (The pound-force is thus roughly the force exerted due to gravity by a mass of one pound at the surface of the Earth.)
Though pounds-force had been used in low-precision measurements since the 18th century, they were never well-defined units until the 20th century. It was in 1901 when the CGPM first adopted a standard acceleration of gravity for the purpose of defining grams-force and kilograms-force, a value often borrowed to define pounds-force, though other values such as 32.16 ft/s² (9.80237 m/s²) have been used as well. If the metric value of exactly 9.80665 m/s², or approximately 32.174 05 ft/s², is used this gives a force of exactly 4.4482216152605 newtons for one pound-force.
See also
- pound (weight) for a more complete discussion of customary units of force and mass.
- pound-force per square inch for a unit of pressure
- foot-pound force, a unit of work, energy, or torque