re metric vs english in apr pixel kodak com dj ekcolor ssd kodak com dave jones writes keith mancus mancus sweetpea jsc nasa gov wrote bruce dunn mindlink bc ca bruce dunn writes si neatly separates the concepts of mass force and weight which have gotten horribly tangled up in the us system this is not a problem with english units a pound is defined to be a unit of force period there is a perfectly good unit called the slug which is the mass of an object weighing lbs at sea level g ft sec of course american military english units perhaps us real english types were once taught that a pound is mass and a poundal is force being that force that causes pound to accelerate at ft s we had a rare olde tyme doing our exams in those units and metric as well american perhaps but nothing military about it i learned mostly slugs when we talked english units in high school physics and while the teacher was an ex navy fighter jock the book certainly wasn t produced by the military poundals were just too flinking small and made the math come out funny sort of the same reason proponents of si give for using that insisting on perfect safety is for people who don t have the balls to live in the real world mary shafer nasa ames dryden fred mccall dseg ti com i don t speak for others and they don t speak for me
