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A pound-foot (lb⋅ft), abbreviated from pound-force foot (lbf · ft), is a unit of torque representing one pound of force acting at a perpendicular distance of one foot from a pivot point. [2] Conversely one foot pound-force (ft · lbf) is the moment about an axis that applies one pound-force at a radius of one foot.
If Imperial units are used, and if torque is in pounds-force feet and rotational speed in revolutions per minute, the above equation gives power in foot pounds-force per minute. The horsepower form of the equation is then derived by applying the conversion factor 33,000 ft⋅lbf/min per horsepower:
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.
This is convenient because one pound mass exerts one pound force due to gravity. Note, however, unlike the other systems the force unit is not equal to the mass unit multiplied by the acceleration unit [11] —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).
Torque; system 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 ...
As the unit name suggests, it is the product of pounds for the unit of force and feet for the unit of displacement. One joule is approximately equal to 0.7376 ft-lbs. [13] [14] Non-SI units of work include the newton-metre, erg, the foot-pound, the foot-poundal, the kilowatt hour, the litre-atmosphere, and the horsepower-hour.
Effective torque (often referred to as wheel torque or torque to the wheels) is a concept primarily associated with automotive tuning. Torque can be measured using a dynamometer. Common units used in automotive applications can include foot-pounds and Newton·meters. [1] The formula for effective torque to the wheels is: [2] Tw = Te * N tf * η ...
The SI units for the torque constant are newton meters per ampere (N·m/A). Since 1 N·m = 1 J, and 1 A = 1 C/s, then 1 N·m/A = 1 J·s/C = 1 V·s (same units as back EMF constant). The relationship between K T {\displaystyle K_{\text{T}}} and K v {\displaystyle K_{\text{v}}} is not intuitive, to the point that many people simply assert that ...