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In engineering and physics, g c is a unit conversion factor used to convert mass to force or vice versa. [1] It is defined as = In unit systems where force is a derived unit, like in SI units, g c is equal to 1.
The pound-force is the product of one avoirdupois pound (exactly 0.45359237 kg) and the standard acceleration due to gravity, approximately 32.174049 ft/s 2 (9.80665 m/s 2).
The inch version of the slug (equal to 1 lbf⋅s 2 /in, or 12 slugs) has no official name, [3] but is commonly referred to as a blob, [12] slinch (a portmanteau of the words slug and inch), [13] [14] slugette, [15] or snail. [16] It is equivalent to 386.0886 pounds (175.1268 kg) based on standard gravity. [3]
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.
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).
The conversion for the poundal is given by 1 pdl = 1 lb·ft/s 2 = 0.138 254 954 376 N (precisely). [1] To convert between the absolute and gravitational FPS systems one needs to fix the standard acceleration g which relates the pound to the pound-force. [citation needed] =
is the standard gravity (in m/s 2 or ft/s 2). In rockets, due to atmospheric effects, the specific impulse varies with altitude, reaching a maximum in a vacuum. This is because the exhaust velocity isn't simply a function of the chamber pressure, but is a function of the difference between the interior and exterior of the combustion chamber .
Of particular significance for this article: 1 lbF, which is here shown as gn * (1 lb) (with only the link to tell us that this is lbM) should also be spelled out as: 32.174 lbM-ft/s^2. Similarly 1 kp = gn 1 kg should be spelled out as 9.8.. kg m/s^2 Hope that this achieves some consensus and can be implemented.