Foot-pound (energy)

Foot-pound
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 pound-force (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 pound-force (lbf) through a linear displacement of one foot. The corresponding SI unit is the joule.

Usage

The foot-pound is often used to specify the muzzle energy of a bullet in small arms ballistics, particularly in the United States.

"Foot-pound" is sometimes also used as a unit of torque (see pound-foot (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 pound-force is equivalent to:

  • 1.355 817 948 331 400 4 joules
  • 13558179.483314004 ergs
  • about 1.285×10−3 British thermal units
  • 0.323832 calories
  • 8.462238×10+18 eV = 8.462238 EeV = 8.462238×10+9 GeV

Power

1 foot pound-force per second is equivalent to:

Related conversions:

  • 1 watt44.25372896 ft⋅lbf/min = 0.737562149333 ft⋅lbf/s
  • 1 horsepower (mechanical) = 33,000 ft⋅lbf/min = 550 ft⋅lbf/s

See also

References

  1. Budynas, Richard G.; Nisbett, J. Keith (2014-01-27). Mechanical Engineering Design. McGraw Hill Education. ISBN 978-0073529288. (Subscription required (help)).


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