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Similarly, an inch-pound (or pound-inch) is the torque of one pound of force applied to one inch of distance from the pivot, and is equal to 1 ⁄ 12 lbf⋅ft (0.1129848 N⋅m). It is commonly used on torque wrenches and torque screwdrivers for setting specific fastener tension.
Systems of measure either define mass and derive a force unit or define a base force and derive a mass unit [1] (cf. poundal, a derived unit of force in a mass-based system). A slug is defined as a mass that is accelerated by 1 ft/s 2 when a net force of one pound (lbf) is exerted on it. [2]
In the US, torque is most commonly referred to as the foot-pound (denoted as either lb-ft or ft-lb) and the inch-pound (denoted as in-lb). [ 17 ] [ 18 ] Practitioners depend on context and the hyphen in the abbreviation to know that these refer to torque and not to energy or moment of mass (as the symbolism ft-lb would properly imply).
In some contexts, the term "pound" is used almost exclusively to refer to the unit of force and not the unit of mass. In those applications, the preferred unit of mass is the slug, i.e. lbf⋅s 2 /ft. In other contexts, the unit "pound" refers to a unit of mass. The international standard symbol for the pound as a unit of mass is lb. [8]
unit code symbol or abbrev. notes conversion factor/N⋅m combinations Industrial: SI: Newton-metre: Nm N⋅m 1 Nm lbft; Nm lbfft; Non-SI metric: kilogram-metre: kgm kg·m 9.80665 Imperial & US customary: pound-foot: lbft lb⋅ft Pound-inch (lb.in) is also available 1.3558 Scientific: SI: newton metre: Nm N⋅m 1 Nm lbft; Nm lbfft; Non-SI ...
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).
pound (avoirdupois) per cubic foot lb/ft 3: ≡ lb/ft 3: ≈ 16.018 463 37 kg/m 3: pound (avoirdupois) per cubic inch lb/in 3: ≡ lb/in 3: ≈ 2.767 990 471 × 10 4 kg/m 3: pound (avoirdupois) per gallon (imperial) lb/gal ≡ lb/gal ≈ 99.776 372 66 kg/m 3: pound (avoirdupois) per gallon (US fluid) lb/gal ≡ lb/gal ≈ 119.826 4273 kg/m 3 ...
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.