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Path: utzoo!watmath!clyde!burl!ulysses!allegra!mit-eddie!godot!harvard!seismo!mcvax!fons
From: fons@mcvax.UUCP (Fons Kuijk)
Newsgroups: net.physics
Subject: Re: Floating a battleship in a gallon of water
Message-ID: <6258@mcvax.UUCP>
Date: Mon, 17-Dec-84 20:46:17 EST
Article-I.D.: mcvax.6258
Posted: Mon Dec 17 20:46:17 1984
Date-Received: Wed, 19-Dec-84 02:19:48 EST
References: <27@daisy.UUCP> <6235@mcvax.UUCP> <1301@hao.UUCP>
Reply-To: fons@mcvax.UUCP (Fons Kuijk)
Distribution: net
Organization: CWI, Amsterdam
Lines: 45
Summary: 



In article <1301@hao.UUCP> hull@hao.UUCP (Howard Hull) writes:

>	"If an object is freely suspended in a liquid, it is buoyed up
>	 by a force equal to the weight of the displaced liquid, or its
>	 virtual equivalent."

As far as I am concerned that's about the same as I wrote in my article.

>So as you can see, I AM STILL serious about requiring the 100,000 tons of
>water to be there even if it is in a virtual form, or as you put it, not
>"really" there.  Please let me apollogize in advance if I confused anyone
>by my incomplete statement of the situation.

Call it virtual and everything turns out to be possible!

>So now I have a question.  If we now wish to squeeze all of the water out of
>the gap between the battleship and trough wall, what force pressing down on
>the ship will be required to do so?  If we can get that question answered,
>then we can find an answer to the original question in its proper context...
>The original question was "how can the water hold up something greater than
>its own weight".  This would seem to be a question of fundamental structure
>were it not for the degree of freedom allowed by the width of the space
>between the ship and the trough.

So you are looking for the two balancing forces.
That should not be to diffecult.
Assume the ship is 1/10 inch above the trough. Then it takes 1/10 inch of
lowering the ship. The force needed for that equals the gravitational force
of the extra volume of the ship below the water level in the lowered position.
In our case that is exactly the water that was in the trough.

You can imagine that this is what you'd expect, because in that case,
the total vertical force on the wall of the trough has not changed!

Of course you can reduce the force after sqeezing out the water, provided
the water cannot return.

About the question of fundamental structure, well we've seen enough of that
by now.
---
No joke                                        Fons Kuijk
No graphics                                    ...mcvax!fons
No maxim [for insiders:-)]