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From: hull@hao.UUCP (Howard Hull)
Newsgroups: net.physics
Subject: Re: Floating a battleship in a gallon of water
Message-ID: <1296@hao.UUCP>
Date: Sun, 9-Dec-84 11:47:06 EST
Article-I.D.: hao.1296
Posted: Sun Dec  9 11:47:06 1984
Date-Received: Tue, 11-Dec-84 03:19:42 EST
References: <27@daisy.UUCP>
Distribution: net
Organization: High Altitude Obs./NCAR, Boulder CO
Lines: 26

> Something that I have found amusing is the fact that a ship can float in a
******Change "float in" to "can be supported in" and I'll buy it.******
> container of water which only contains a VERY small amount of water.
>
> For example, if a container is shaped so that it is 1/10 inch away from the
******I will spare us by not bothering to calculate how many gallons of water
******will be in a 1/10 inch thick layer of water the area of the ship's hull.
> ship on all sides (and the bottom),
> then the water filling that small gap will hold it up.
******There may be situations in which this is true, but usually it wouldn't be.
> The counter-intuitive fact is that
> the weight of the water can be *much* less than the ship's weight.
******Arrgh. Here we go.  The principle of Archimedes would, for the purposes
of this discussion, best be stated:  "When an object is freely suspended in
a liquid, the object will be buoyed up by a force equal to the weight of the
displaced liquid."  Therefore, if you have a 100,000 ton ship, you are going
to need 100,000 tons of water for it to displace; otherwise, a force of some
other description will be found to be responsible for supporting the ship.
> How is it that the water can hold up a ship which weighs
> more than the water?                                             -dbell-
The layer of water has to be thin enough that small scale molecular interaction
between the water and the container transfers the force represented by the
weight of the ship directly to the walls of the container.  Then the water is
between a rock and a hard place, and has no choice but to support the ship.
								Howard Hull
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