Foot-pound (energy) Foot-pound (energy) The foot pound-force (symbol: ft⋅lbf or ft⋅lb) 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. 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 also used as a unit of torque (see "pound-foot (torque)"). In the United States this unit is often
Rad (unit) in the latest NIST definition. Even where the standard medium is fully defined, the ionizing energy is often not precisely known. In 1940, British physicist Louis Harold Gray, who had been studying the effect of neutron damage on human tissue, together with William Valentine Mayneord and John Read published a paper in which a unit of measure, dubbed the ""gram roentgen"" (symbol: gr) defined as "that amount of neutron radiation which produces an increment in energy in unit volume of tissue equal to the increment of energy produced in unit volume of water by one roentgen of radiation" was proposed.