[net.physics] floating a battleship in a gallon of water: here's how it works:

merrill@5140.DEC (12/13/84)

All the ship has to do is to DISPLACE 100,000 tons of water.  Thus the
volume of ship UNDER the water line multiplied by the weight of water
must (and will) equal the weight of the ship (unless it's sinking/sunk).


My graphics may not be as neat but...

-------------
| ship      |
|100,000 ton|
 \         /
  \       /
   \     /
    \   /


\water    /
 \100,000/
  \tons /
   \   /
  

But maybe you want to know where the water went when it got displaced?
It went byebye, over the hill, you won't miss it!  It's the WATER PRESSURE
that holds the ship up.  That's why BIG ships have THICK hulls.  It even
works for Shallow ships:
|----------------------------------|
|100,000 tons of ship              |
------------------------------------
(barge actually!@)

|100,000 tons of water displaced   |
------------------------------------
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^  water pressure * area = 100,000 tons

Note that the pressure of water per foot of depth (lbs/ft*ft /ft)
is the same as the density of water (lbs/ft*ft*ft).  [Prove it.]

thus volume h*l*w displaced times density 
	=
area l*w times pressure h*density