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In Reply to: Re: Torque units.. posted by Mikael Borgström on September 09, 2000 at 12:11:58:
In the MKS system, you've chosen mass, length and time as the fundamental quantities and units defined in terms of these standards. Force appears as a derived quantity, determined from F=ma.
In the British engineering system of units, however, force, length and time are chosen as the fundamental quantities, and mass is a derived quantity. In this system, mass is determined from m=F/a.
Torque may be commonly referred to in British units as "foot-pounds", but scientifically it is "pound-foot or pound-feet", and most texts refer to it that way. So, we're still talking about the same force applied along the same vector, whether you call that force pounds, newtons, dynes, grains or poundals; or call that vector by meters, feet, chains, rods, ropes or furlongs.
So, for pound (force) take 1 Lb = (0.4536 kg)(9.806 m/sec^2) = 4.448 newtons
OK math aside --------
Now then, don't be so chauvinistic about the metric system, unless you accept that it's just as arbitrary as the British (English) system. The metric system was the brainchild of one Gabriel Mouton, vicar of Lyons, in 1670. It didn't rise to prominence until over 100 years later, in 1790 in the midst of the French Revolution. The Revolutionary Convention decided to purge the old system of weights and measures along with the monarchy, and proposed a new standard, the meter. It was to be one ten-millionth of an earth quadrant, namely, one ten-millionth of the distance from the equator to the North Pole measured along the land meridian than runs through Paris. Some standard. Needless to say, trying to measure that distance was too much, so they decided to use the distance from Dunkirk to Barcelona (one ninth of a quadrant). After seven years of pacing off this distance, they multiplied by nine, divided by 10 million and behold…..
Well, as it turns out, they undershot by about two parts in ten thousand. This is probably no more accurate than the old standard for the Scottish inch - the average width of three men's thumbs - or the German foot - the average length of the shoes of sixteen men leaving church one Sunday morning in the seventeenth century. Accurate or not, the meter defined the liter (1/10 meter cubed), which defined the kilogram (the weight of one liter of water at 4 C.), etc. etc.
Metric measure became law in France on December 10, 1799, and it's use compulsory on January 1, 1840. By 1911, the metric system had done something that Napoleon could never do, it invaded and conquered nearly the entire world.***
***The preceding was culled from a number of different sources.
So, it's still a matter of frame of reference. I use both systems everyday. Just remember the words of the wise old man:
"There are two kinds of fools, one says 'This is old, and therefore good', and the other says 'This is new, and therefore better'."
Best wishes to all,
Stan C.
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