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# Re: Vector Rules

From: Samuel Penn <sam@b...>
Date: Thu, 09 Oct 1997 18:46:07 +0100
Subject: Re: Vector Rules
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Status: RO

In message
<Pine.OSF.3.96.971007115245.1520C-100000@zeorymer.alf.dec.com>
Alexander Williams <thantos@alf.dec.com> wrote:

> Tell you what, let's go down to the nearest lake.  To you, I'll float
a 8'
> long, 1' thick oak log.  I'll take a 8" long, 1" thick oak twig.  You
turn
> yours in the water, I'll turn mine.  One rotation, then stop.  Reverse
> that motion.	Repeat a hundred times.  Let's see who's out of breath
and
> wishing he hadn't been sitting hip-deep in the lake.

Not quite a fair comparison - the oak log has much greater
friction acting on it. In space, there is none of that.
You've also got moments of inertia to factor in - the log
is longer, so it's a better lever.

In fact, if you want to be picky, both the log and the twig
would take exactly the same amount of effort.

Of course, while a push on the twig rotates it at 90 degrees
a second, the same push on the log starts it rotating at
maybe 1 degree a second. It takes longer, but no more
effort.

>
> Entropy always wins and Inertia is His Handmaiden.  It takes a /huge/
> amount of thrust to rotate a billion tonne super dreadnaught.  Don't
be
> silly.  It takes just as much thrust to sweep it through one complete
> rotation as to move it one ship-length, I'd imagine.	One of our
> numericists can crank the exact numbers.  :)

You could always use damn big fly wheels (rotate wheels one
way, ship rotates the other). Then you don't need _any_
thrust. :)

--
Be seeing you,
Sam.
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