Who do big boats/ships float, and don't sink?

Question

Who do big boats/ships float, and don't sink?

Answer 1

Short answer: Boats float because they can displace an amount of water that is equal to or greater than their own weight.

Answer 2

Buoyancy.

The displaced weight of the water is the force upwards onto the boat/ship. Water weighs in at 8.35 lbs per gallon and there are 7.48 gallons per cubic foot. The ship will simply displace just enough volume to equal  the weight of the ship.

Answer 3

All of the above answers are good, but I'll try to simplify bouncy for you.

Fill a sink with water.  Take a large plastic cup and push it with the open end up as far down as you can without letting water get in it.  You will feel the cup pushing up on your hand.  Right??   This force you are feeling will be the same as if you filled the cup with water and held it in your hand. The weight of the water in the cup is how much weight the cup, if it were a boat, could hold.

If you weighed the cup filled with water, we will assume the cup itself is so light it doesn't weigh anything, that is how much weight the cup will hold if floating in water.  So if the cup of water weighed 10 pounds, you could put 9.9 pounds of rocks in the cup and it will still float.

So the bigger the ship and the more weight,  the bigger the cup that's under water.

Answer 4

Believe it or not, they use to make large ships with concrete hulls. I saw one as a kid on the NJ coast that ran a ground.

Sorry I got off on some other subject, but see concrete hull ships here.

http://www.unmuseum.org/concrete.htm