Pat Naughtin wrote in USMA 23356:
I, too, was taught about fps and at the time I was informed that this was an alternative 'system' to the metric systems cgs and mks. Then almost without a pause I was taught the foot-slug-second 'system but this was never
I believe that the slug as a unit of mass was invented by the aeronautical engineers. They clung to the pound-force, because historically gravity was the only force civil engineers were concerned with. The aeronautical engineers had to deal with accelerations quite different from the acceleration due to gravity, and so they invented the slug = 32.2 pounds-mass. Thus
force (pounds-force) = mass x acceleration (slugs x feet/second squared).
I first met the slug at the Royal Aircraft Establishment. Physicists were quite happy with the pound-mass so they invented the poundal = (1/32.2) pound-force. Thus:
force (poundals) = mass x acceleration (pounds-mass x feet/second squared).
Joseph B. Reid
17 Glebe Road West
Toronto M5P 1C8 Telephone 416-486-6071
