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Re: [Amps] Amps Digest, Vol 32, Issue 12: Metric system

To: amps@contesting.com
Subject: Re: [Amps] Amps Digest, Vol 32, Issue 12: Metric system
From: gdaught6@stanford.edu
Date: Thu, 04 Aug 2005 20:07:51 -0700
List-post: <mailto:amps@contesting.com>
OK, as a physicist I feel compelled to jump into this a little bit.

> Then there is pressure measurement. kilogram squared.  Fer instance:
> 40 lbs or so of oil pressure is a little over 5 kg/sq. This is not an
> exact figure but close enough. 

Pressure is in units of force per unit area.  "40 lbs" of oil 
pressure commonly means "40 pounds [a force] per square inch [an 
area]."  I don't even know what "kilogram squared" and "kg per 
square" [a mass per square what?] mean.  

A kilogram exerts a downward force due to gravity of about 2.2 pounds 
at the surface of the earth, so 5 kilograms exerts a gravitational 
force of 11 pounds.  Sometimes we talk about "kilograms of force" 
because we're too lazy to multiply by the acceleration of gravity.  
Just for a the heck of it, a square inch is a bit over 6 square 
centimeters.

This sort of vagueness doesn't require the metric system, and 
certainly has very little to do with amplifiers,* so I apologize.  
I'm done.

73,

*Although we often want to know about the cooling air through our 
tube fins, which we can estimate by measuring the pressure drop 
across the tube's cooler, and consulting the tube manufacturer's data 
sheet.

George T. Daughters, K6GT



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