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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).
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.
The pound or pound-mass is a unit of mass used in both the British imperial and United States customary systems of measurement.Various definitions have been used; the most common today is the international avoirdupois pound, which is legally defined as exactly 0.453 592 37 kilograms, and which is divided into 16 avoirdupois ounces. [1]
The pound-force is the product of one avoirdupois pound (exactly 0.45359237 kg) and the standard acceleration due to gravity, approximately 32.174049 ft/s 2 (9.80665 m/s 2). [ 5 ] [ 6 ] [ 7 ] The standard values of acceleration of the standard gravitational field ( g n ) and the international avoirdupois pound (lb) result in a pound-force equal ...
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).
Both energy and torque can be expressed as a product of a force vector with a displacement vector (hence pounds and feet); energy is the scalar product of the two, and torque is the vector product. Although calling the torque unit "pound-foot" has been academically suggested, both are still commonly called "foot-pound" in colloquial usage.
A fire hydrant marked as 3-inch. The inch (symbol: in or ″) is a unit of length in the British Imperial and the United States customary systems of measurement.It is equal to 1 / 36 yard or 1 / 12 of a foot.
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.