Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/17/84; site hao.UUCP Path: utzoo!watmath!clyde!burl!ulysses!allegra!mit-eddie!godot!harvard!seismo!hao!hull 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 {ucbvax!hplabs | allegra!nbires | harpo!seismo } !hao!hull