Return to index: [Subject] [Thread] [Date] [Author]

Re: Low Concrete Quality

[Subject Prev][Subject Next][Thread Prev][Thread Next]
>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"
>for both?
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)
http://www.skypoint.com/~chrisw


* 
*   This email was sent to you via Structural Engineers 
*   Association of Southern California (SEAOSC) server. To 
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you 
*   send to the list is public domain and may be re-posted 
*   without your permission. Make sure you visit our web 
*   site at: http://www.seaint.org