What Makes a Ship Float in Water While a Steel bar Sinks?
Historical records show that floating of an object was first introduced by Archimedes. He theorized that if an object is equal to the volume or weight of the water it displaces, the object will rise up in water and float. So, if a ship has a weight of 1,000 kilograms, it has to displace 1,000 kilograms of water in order to float.
This is the Law of Buoyancy. Anything that has a weight equal to the amount of water it displaces will float in water. If the ship has been made in such a way that it can displace the amount of water equal to its weight or even more of its weight, then the ship will float in water. The reason is because a major interior part of the ship is made up of air which is less dense than water.
On the other hand, a steel bar is solid steel that has no space to displace water, therefore, it will sink. The ship which has a combination of steel and air has lesser density than the water it displaces. Therefore, a very small portion of the ship has to submerge in the water before the water can displace the weight of the ship.
If you submerge a box measuring 1 foot to the water, the reading that will appear in the gauge estimated at 0.44 psi. This means that the bottom of the box is being pushed upward by the pressure of water. Therefore, if the box is 1 sq. ft. and it is submerged to a depth of 1 ft., the bottom of the box will be pushed by the pressures of water measuring 62 pounds.
It is actually the pressures of water that push the bottom of the ship that enables the ship to float. The part of the ship that is submerged in water has corresponding pressure of water that is pushing it upward and this combination of pressures allow the ship to float.
If you notice, when anything floats in the water, part of its bottom is submerged in the water. As the object sinks a little, it displaces the water until that volume of water weighs equally with the weight of the object. If the weight of the object you are trying to float is so heavy and solid, there is no way that it can push or displace enough water in order to float. In this case you can expect that it will absolutely sink.
Try this experiment to show you how buoyancy works. Place a ship made of plastic on the surface of the water. Observe how the empty object sinks. Observe how it sinks deeper when you put some pennies to it until the water reaches the top wherein the plastic ship will sink.
Float a balloon in water; it will not sink deeply because the balloon is lighter than water. If you put balloons above the water, you will notice that a small part of the balloon is underwater and the rest is floating.
Therefore, buoyancy of an object does not depend on the weight at all whether it floats or it sinks. Floating and sinking depends on how much amount of water an object can displace in order to float.