Search results
Results From The WOW.Com Content Network
The standard acceleration of gravity or standard acceleration of free fall, often called simply standard gravity and denoted by ɡ 0 or ɡ n, is the nominal gravitational acceleration of an object in a vacuum near the surface of the Earth. It is a constant defined by standard as 9.806 65 m/s 2 (about 32.174 05 ft/s 2).
Units for other physical quantities are derived from this set as needed. In English Engineering Units, the pound-mass and the pound-force are distinct base units, and Newton's Second Law of Motion takes the form = where is the acceleration in ft/s 2 and g c = 32.174 lb·ft/(lbf·s 2).
[2] [3] At different points on Earth's surface, the free fall acceleration ranges from 9.764 to 9.834 m/s 2 (32.03 to 32.26 ft/s 2), [4] depending on altitude, latitude, and longitude. A conventional standard value is defined exactly as 9.80665 m/s² (about 32.1740 ft/s²). Locations of significant variation from this value are known as gravity ...
In unit systems where force is a derived unit, like in SI units, g c is equal to 1. In unit systems where force is a primary unit, like in imperial and US customary measurement systems , g c may or may not equal 1 depending on the units used, and value other than 1 may be required to obtain correct results. [ 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 ]
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).
In SI units, this acceleration is expressed in metres per second squared (in symbols, m/s 2 or m·s −2) or equivalently in newtons per kilogram (N/kg or N·kg −1). Near Earth's surface, the acceleration due to gravity, accurate to 2 significant figures, is 9.8 m/s 2 (32 ft/s 2).
Since a pound of force (pound force) accelerates a pound of mass at 32.174 049 ft/s 2 (9.80665 m/s 2; the acceleration of gravity, g), we can scale down the unit of force to compensate, giving us one that accelerates 1 pound mass at 1 ft/s 2 rather than at 32.174 049 ft/s 2; and that is the poundal, which is approximately 1 ⁄ 32 pound force.