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From: fred@mnetor.UUCP (Fred Williams)
Newsgroups: net.physics
Subject: Re: Newton's Second Law
Message-ID: <1182@mnetor.UUCP>
Date: Fri, 5-Jul-85 09:56:34 EDT
Article-I.D.: mnetor.1182
Posted: Fri Jul  5 09:56:34 1985
Date-Received: Fri, 5-Jul-85 11:10:07 EDT
References: <9255@Glacier.ARPA>
Reply-To: fred@mnetor.UUCP (Fred Williams)
Distribution: net
Organization: Computer X (CANADA) Ltd., Toronto, Ontario, Canada
Lines: 26
Summary: 

In article <9255@Glacier.ARPA> wong@Glacier.ARPA (Man Wong) writes:
>What is the content of Newton's Second Law? Is it a definition? Can definitions
>be called physical laws?
>
>Please help!

	Newton's second law really defines a relationship between mass,
force, and the "time rate of change of momentum". I believe Newton
himself expressed it as;

							dp
					F	=  ----
							dt

	It is interesting to note that this holds true even when
relativistic effects are taken into account. It resolves to "ma"
when the mass is constant. 
	I do not mean to imply that Newton anticipated Einstein, merely
that he knew well the calculus which he invented and it's implications
in the real world. 

	If you are looking for the definitions of "mass" and "force", check
any good physics text.

Cheers,		Fred Williams