Units Was: Where is balance 277

alt.folklore.computers

Please specify which system of units you are using. There's a choice of absolute or gravitational units. The Imperial gravitational units have the slug as unit of mbutt, and pound as force, absolute has lb as the unit of mbutt and poundal as force. The "g" has to go somewhere: either have the lbf for force, and a 32lbm slug, or have a 1lbm which weighs 32 poundal. Mix them if you wish, use lbf and lbm together, just watch out for the "g".

(As an engineer, I always use the subscripted notation of lbm, lbf if there's any possibility of confusion, guess I'm a revisionist. )

It's just that many non-revisionists wouldn't recognise a poundal if one kicked them up their backsides. :)

Looking at a 1914ish Leftpondian Mechanical Engineers' Handbook (once the property of my grandfather) I find "To avoid uncertainty it is desirable to call the units "pound force" &etc." Similar recommendation for "kilogram force" &etc: the metric types hadn't got round to defining the Newton then, so the book calls it a "metric slug". We revisionists have been working at this problem for 3 generations, at least. :)

I'm sure that Newton had it all worked out.

For me, it all changed in the 50s, when I was about 16. Out with the poundal (and the dyne), and in with the slug (and the Newton). I expect that my generation of teachers who had to teach both systems, (and deal with temporarily confused kids) were the last generation of teachers to understand this topic. Certainly the present generation of Brit schoolteachers *do not* understand.

Revisionist regards,

David P.