Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83 (MC840302); site mcvax.UUCP 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: <6235@mcvax.UUCP> Date: Tue, 11-Dec-84 20:12:47 EST Article-I.D.: mcvax.6235 Posted: Tue Dec 11 20:12:47 1984 Date-Received: Thu, 13-Dec-84 02:21:03 EST References: <27@daisy.UUCP> Reply-To: fons@mcvax.UUCP (Fons Kuijk) Distribution: net Organization: CWI, Amsterdam Lines: 95 Summary: In article <27@daisy.UUCP> dbell@daisy.UUCP (David I. Bell) writes: > > | || | > A COUNTER-INTUITIVE FACT | /||\ | > | ------------------ | >Something that I have found amusing | | | | >is the fact that a ship can float in a \ \ / / >container of water which only contains \~~\ /~~/ >a VERY small amount of water. \~~\ SHIP /~~/ > \~~\ /~~/ >For example, if a container is shaped so \~~\ /~~/ >that it is 1/10 inch away from the ship on \~~\ /~~/ >all sides (and the bottom), then the water \~~\ /~~/ >filling that small gap will hold it up. =====> \~~\--/~~/ > \~~~~~~/ >The counter-intuitive fact is that the weight of \~~~~/ >the water can be *much* less than the ship's weight. \--/ > >How is it that the water can hold up a ship which weighs >more than the water? -dbell- Remember this from long ago? | | | | \ / | | \~~~~~~~~~~~~~~~~~~~~/ |~| \~~~~~~~~~~~~~~~~~~/ |~| \~~~~~~~~~~~~~~~~/ |~| \~~~~~~~~~~~~~~/ |~| \~~~~~~~~~~~~/ |~| \~~~~~~~~~~/ |~| \~~~~~~~~/ |~| \~~~~~~/ |~| \~~~~/ |~| \~~/ |~| |~~|_________________|~| |~~~~~~~~~~~~~~~~~~~~~~| ------------------------ What is the difference compared to | || | | /||\ | | ------------------ | | | | | | | \ \ / / | | \~~\ /~~/ |~| \~~\ SHIP /~~/ |~| \~~\ /~~/ |~| \~~\ /~~/ |~| \~~\ /~~/ |~| \~~\ /~~/ |~| \~~\--/~~/ |~| \~~~~~~/ |~| \~~~~/ |~| \~~/ |~| |~~|_________________|~| |~~~~~~~~~~~~~~~~~~~~~~| ------------------------ It is all a matter of balancing forces. ------------------------------------------------------------ |> 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. ------------------------------------------------------------ You are not serious about really having to displace 100,000 ton of water? You might as well start with a container containing a small amount of water in it. By inserting the ship, the water will rise. This will cause an upward force due to pressure on the ships surface. Now in this system during insertion, not only the surface of the ship below water level will increase, but also the pressure wil rise due to rising of the water. It is no surprise that the total upward force (being the total sum of local pressure*surface area) equals the weigth of the water that would occupy the same volume that the part of the ship below water level occupies. The system behaves much like a hydrolic lever, which to some people already is thought to be counter intuitive. But apart from that, due to the v-shape of the ship and the container, the system does not behave linear, which makes it amusing indeed. --- No joke Fons Kuijk No graphics ...mcvax!fons No maxim [for insiders:-)]