Slug (unit)

The slug is a derived unit of mass in a weight-based system of measures, most notably within the British Imperial measurement system and the United States customary measures system. Systems of measure either define mass and derive a force unit or define a base force and derive a mass unit^[1] (cf. poundal, a derived unit of force in a force-based system). A slug is defined as a mass that is accelerated by 1 ft/s² when a net force of one pound (lbf) is exerted on it.^[2]

${\displaystyle 1~{\text{slug}}=1~{\text{lbf}}{\cdot }{\frac {{\text{s}}^{2}}{\text{ft}}}\quad \Longleftrightarrow \quad 1~{\text{lbf}}=1~{\text{slug}}{\cdot }{\frac {\text{ft}}{{\text{s}}^{2}}}}$

One slug is a mass equal to 32.17405 lb (14.59390 kg) based on standard gravity, the international foot, and the avoirdupois pound.^[3] In other words, at the Earth's surface (in standard gravity), an object with a mass of 1 slug weighs approximately 32.17405 lbf or 143.1173 N.^[4][5]