A poundal is the force needed to accelerate a one-pound mass one foot per second per second.
The units of slug and poundal are designed to avoid a constant of proportionality in Newton's Second Law.
The conversion for the poundal is given by 1 pdl = 1 lb�ft / s 2 = ( precisely ).
Expressions derived using poundals for force and lb for mass ( or lbf for force and slugs for mass ) have the advantage of not being tied to conditions on the surface of the earth.
Note : Slugs ( 32.174 049 lb ) and poundals ( 1 / 32.174 049 lbf ) are never used in the same system, since they are opposite solutions of the same problem.
Since one poundal equals about 4.4 newtons, it would seem that such an error would be readily detected, but Hinners said this was not the case because the thrusters contributed only a little to the orbit.
An alternative unit of force in a different foot-pound-second system, the absolute fps system, is the poundal, defined as the force required to accelerate a one-pound mass at a rate of one foot per second squared.
Specifically, computing " F " = " ma " on the moon or in deep space as poundals, lb�ft / s 2 or lbf = slug�ft / s 2, avoids the constant tied to acceleration of gravity on earth.
:: : : In the UK in the 60s / 70s, we were taught that a pound is a unit of mass, and its associated force is a poundal .-- talk ) 11 : 43, 18 January 2015 ( UTC)