Footpound (energy)
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Footpound  

Unit system  English Engineering units and British Gravitational System 
Unit of  Energy 
Symbol  ft⋅lbf 
Unit conversions  
1 ft⋅lbf in ...  ... is equal to ... 
SI units  1.355818 J 
CGS units  13,558,180 erg 
The foot poundforce (symbol: ft⋅lbf or ft⋅lb)^{[1]} is a unit of work or energy in the Engineering and Gravitational Systems in United States customary and imperial units of measure. It is the energy transferred upon applying a force of one poundforce (lbf) through a linear displacement of one foot. The corresponding SI unit is the joule.
Usage
The footpound is often used to specify the muzzle energy of a bullet in small arms ballistics, particularly in the United States.
"Footpound" is also used as a unit of torque (see poundfoot (torque)). In the United States this unit is often used to specify, for example, the tightness of a bolt or the output of an engine. Although they are dimensionally equivalent, energy (a scalar) and torque (a vector) are distinct physical quantities. 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.
Conversion factors
Energy
1 foot poundforce is equivalent to:
 1.355 817 948 331 400 4 joules
 558179.483314004 13ergs
 about ×10^{−3} 1.285British thermal units
 832 0.323calories
 238×10^{+18} 8.462eV = 238 8.462EeV = 238×10^{+9} 8.462GeV
Power
1 foot poundforce per second is equivalent to:
 1.355817948 watts
 18×10^{−3} 1.8horsepower
Related conversions:
 1 watt ≈ 72896 ft⋅lbf/min = 44.253562149333 ft⋅lbf/s 0.737
 1 horsepower (mechanical) = 33,000 ft⋅lbf/min = 550 ft⋅lbf/s
See also
References
 ^ Budynas, Richard G.; Nisbett, J. Keith (20140127). Mechanical Engineering Design. McGraw Hill Education. ISBN 9780073529288. (Subscription required (help)).
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