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The electrostatic and electromagnetic systems are derived from units of length and force, mainly. As such, these are ready extensions of any system of containing length, mass, time. Stephen Dresner [7] gives the derived electrostatic and electromagnetic units in both the foot–pound–second and foot–slug–second systems. In practice, these ...
Since a pound of force (pound force) accelerates a pound of mass at 32.174 049 ft/s 2 (9.80665 m/s 2; the acceleration of gravity, g), we can scale down the unit of force to compensate, giving us one that accelerates 1 pound mass at 1 ft/s 2 rather than at 32.174 049 ft/s 2; and that is the poundal, which is approximately 1 ⁄ 32 pound force.
One slug is a mass equal to 32.17405 lb (14.59390 kg) based on standard gravity, the international foot, and the avoirdupois pound. [3] In other words, at the Earth's surface (in standard gravity), an object with a mass of 1 slug weighs approximately 32.17405 lbf or 143.1173 N. [ 4 ] [ 5 ]
The foot-poundal (symbol: ft-pdl) is a unit of energy, introduced in 1879, that is part of the Absolute English system of units, which itself is a coherent subsystem of the foot–pound–second system. [1] The foot-poundal is equal to 1/32.174049 that of the more commonly used foot-pound force.
The pound of force or pound-force (symbol: lbf, [1] sometimes lb f, [2]) is a unit of force used in some systems of measurement, including English Engineering units [a] and the foot–pound–second system. [3] Pound-force should not be confused with pound-mass (lb), often simply called "pound", which is a unit of mass; nor should these be ...
An alternative unit of force in a different foot–pound–second system, the absolute fps system, is the poundal, defined as the force required to accelerate a one-pound mass at a rate of one foot per second squared. [58] The pound-force has a metric counterpart, less commonly used than the newton: the kilogram-force (kgf) (sometimes kilopond ...
The nit (nt) is a unit of luminance equal to one candela per metre squared (1 cd⋅m −2). The lambert (L) is a unit of luminance equal to 10 4 /π cd⋅m −2. The lumerg is a unit of luminous energy equal to 10 −7 lumen-seconds (100 nlm s). The talbot (T) is a unit of luminous energy equal to one lumen-second (1 lm⋅s).
Units for other physical quantities are derived from this set as needed. In English Engineering Units, the pound-mass and the pound-force are distinct base units, and Newton's Second Law of Motion takes the form = where is the acceleration in ft/s 2 and g c = 32.174 lb·ft/(lbf·s 2).