Re: defining laws in isolation or 'no other force acting'

Gary Oberbrunner <[email protected]> Mon, 20 Jan 2014 17:11:09 -0500
Newsgroups	gmane.science.physics.fabric-of-reality
Message-ID	<CAFChFyg_pawLqo+nkqt25M1OM23ii-j-eq7+pdmNgPz5wVNB_w@mail.gmail.com>
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On Sun, Jan 19, 2014 at 2:26 AM, <hibbsa-/[email protected]> wrote:

> the reasoning seems to reverse quite easily, such that the second law
> derives from the first.


The first law doesn't specify the relationship between force and
acceleration (except that there is one).  For instance, F=m*a^2 would also
lead to bodies at rest staying at rest and bodies in motion staying in that
state of motion.  (There's no acceleration in either case.)  So you can't
derive the second law from the first, only the other way.

-- 
Gary


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      <p>On Sun, Jan 19, 2014 at 2:26 AM, &lt;hibbsa-/[email protected]&gt; wrote:<br>
<br>
&gt; the reasoning seems to reverse quite easily, such that the second law<br>
&gt; derives from the first.<br>
<br>
The first law doesn&#39;t specify the relationship between force and<br>
acceleration (except that there is one).  For instance, F=m*a^2 would also<br>
lead to bodies at rest staying at rest and bodies in motion staying in that<br>
state of motion.  (There&#39;s no acceleration in either case.)  So you can&#39;t<br>
derive the second law from the first, only the other way.<br>
<br>
-- <br>
Gary<br>
<br>
</p>

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