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From: mann@LaBrea.ARPA
Newsgroups: net.tv.drwho
Subject: re: Re: TARDIS Mass (what is it?) [Full Circle]
Message-ID: <129@LaBrea.ARPA>
Date: Fri, 13-Sep-85 19:08:25 EDT
Article-I.D.: LaBrea.129
Posted: Fri Sep 13 19:08:25 1985
Date-Received: Sun, 15-Sep-85 04:59:17 EDT
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Organization: Stanford University
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> 
> Kilograms are most definately a unit of WEIGHT . . .
> 

You can shout as loud as you want, but that doesn't make you right.  Please
consult an introductory physics textbook before shooting off your mouth.

Mass is a measure of (loosely speaking) the "quantity of matter" in an
object, or its inertia.  Weight is defined as the force exerted on an object
by gravity.  In a constant gravitational field, weight is directly
proportional to mass.

In the SI (metric) system, the basic unit of mass is the kilogram.  Force
(weight) is measured in newtons, where 1 nt = 1 kg-m/sec^2.  In the English
system, the basic unit of mass is the (little-used) slug.  The basic unit of
force (weight) is the pound.  My engineer roommate tells me that the "pound
of mass" (the mass of an object that weighs one pound in Earth's gravity at
sea level) is more commonly used than the slug as a mass unit in the English
system, just to make things more confusing.

In common usage (since most of us spend all our time in a constant
gravitational field), the terms "mass" and "weight" are used
interchangeably, but there is definitely a difference.

	--Tim