how do large ships, ie, container, oil tankers & cruise ships stay afloat?

Answer 1

The total amount of water that they displace (i.e.: push aside) weighs more than the ship itself. The water that is pushed upward by the body of the ship, as it settles down into the water, tries to sink back into its former place because of gravity, but the displaced water cannot because the hull of the ship is in the way. So the water pushes on the ship's hull, producing a net upward force that supports the ship. As long as the ship is less dense overall than an equivalent volume of salt water, the ship will float.

Answer 2

The ship displaces water that is equal in mass to the ship itself. A practical demonstration of this is good, here are two things that you can do.......... First get three plastic containers from the kitchen (one big one, one medium one and one small one), some glass marbles and a set of kitchen scales. Put the medium container inside the large one and fill the medium one with water Right to the top. Float the small container on the water. Add marbles to the small container until it has displaced some water which collects in the large container. Tip the displaced water into the scale pan and weigh it. Poor the water out and weigh the small container with the marbles in it. The two weights will be the same. Do it again with more marbles. Same result. Now get some kitchen foil which is metal, just like a ship. Make a nice little ship shape out of it and show that it floats. Now screw the boat up into a small tight ball. Throw it in the water and show that it sinks.

Answer 3

Archimedes Principle is what you're looking for.

The "floating force" is equal to the volume of liquid the object displaces, multiplied by its density, and by gravity.

Answer 4

Randy G has it right -- That whole upward force by the water is called, 'buoancy'

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Answer 5

Surface tension.

Answer 6

It's all to do with density (mass / volume).