· it is because of the buoyant force exerted by the water to the object which is equal to the weight of the object. this can be calculated using formulas.
· Use the Archimedean Principle, which is :-
"The weight of a body immersed in a fluid is equal to the weight of the fluid displaced."
In practice , tie up a house brick, which weighs about 3kgs. Now suspend it in water on the end of the tie with a weigh scale attached. You will find that the brick now weighs about 2kgs. The remaining mass of 1 kg is the mass of the water displaced.
A ship on the ocean obeys the same principle. The tonnage of water displaced by the hull is much greater than the hull, that is the shape and all the air it contains. Hence it floats.
Archimedes pondered this problem, when one day he got in the bath and noticed that the bath water slopped over the side of the bath (displacement). He jumped up and ran down the street shouting 'Eureka - I have found it'. Hence it is called Archimedes Principle.
· Because of all the empty space within the ship, the ship actually weighs less than the equal amount of water, volume for volume. The ship sinks into the water until an equal amount of water volume is displaced, with the remainder of the ship remaining above water.
· its mostly because of the principles of density and buoyancy
· Archimedes and his buoyancy principle states that a ship will float when the weight of the water it displaces equals the weight of the ship and anything will float if it is shaped to displace its own weight of water before it reaches the point where it will submerge.
This is kind of a technical way of looking at it. A ship that is launched sinks into the sea until the weight of the water it displaces is equal to its own weight. As the ship is loaded, it sinks deeper, displacing more water, and so the magnitude of the buoyant force continuously matches the weight of the ship and its cargo.
Archimedes figured out that the metacenter had to be determined which is a point where an imaginary vertical line (through the center of buoyancy) intersects another imaginary vertical line (through a new centre of buoyancy) created after the ship is displaced, or tilted, in the water.
The center of buoyancy in a floating ship is the point in which all the body parts exactly balance each other and make each other float. In other words, the metacenter remains directly above the center of buoyancy regardless of the tilt of the floating ship. When a ship tilts, one side displaces more water than the other side, and the center of buoyancy moves and is no longer directly under the center of gravity; but regardless of the amount of the tilt, the center of buoyancy remains directly below the metacenter. If the metacenter is above the center of gravity, buoyancy restores stability when the ship tilts. If the metacenter is below the center of gravity, the boat is unstable and capsizes.