To: "SEAOC Newsletter" <seaint(--nospam--at)seaint.org>
Subject: Re: Low Concrete Quality
From: Christopher Wright <chrisw(--nospam--at)skypoint.com>
Date: Fri, 15 Jun 01 19:45:37 -0500
>Not trying to be picky, just trying to understand. How do you differentiate
>between kilogram mass and kilogram force if you are using the symbol "kg"
There was a time when kilogram was used for both force and mass, just
like the term pound was used. The force usage simply meant a force equal
to the force of gravity on the mass of one kilogram.Very sloppy usage but
you could generally sort them out in their context. About the only way I
made sense of it was to hold my node and tell myself that 1 force
kilogram is 2.20462... pounds and make the quantity into actual force
units as fast as possible.
You can still find engineering publications which use kg/mm^2 as a unit
of pressure or stress. My old fluids book (by Streeter, who was no dummy)
quotes values for the universal gas constant of aa.b feet meaning aa.b
foot-pounds(force)/pound(mass). I don't know if rocket people still speak
of specific impulse as aa.b seconds meaning aa.b
pound(force)-second/pound mass. I think dimensional analysis is another
of those lost arts like calculation with logarithms, but it help get a
lot of people through such inconsistencies.
Christopher Wright P.E. |"They couldn't hit an elephant from
chrisw(--nospam--at)skypoint.com | this distance" (last words of Gen.
___________________________| John Sedgwick, Spotsylvania 1864)
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