It seems amazing that huge ocean ships keep afloat and do not sink. If you take a solid piece of metal and put it in water, it will sink immediately. But modern liners are also made of metal. How can you explain their good buoyancy? The fact that the metal hull of the ship is able to stay on the surface of the water is explained by the laws of physics.
Why doesn't the ship sink
The ability to stay on the surface of the water is characteristic not only of ships, but also of some animals. Take at least a water strider. This insect from the Hemiptera family feels confident on the water surface, moving along it with sliding movements. This buoyancy is achieved due to the fact that the tips of the feet of the water strider are covered with hard hairs that are not wetted by water.
Scientists and inventors hope that in the future, humans will be able to create a vehicle that will move on water according to the principle of a water strider.
But the principles of bionics do not apply to traditional ships. Any child familiar with the basics of physics can explain the buoyancy of a ship made of metal parts. As Archimedes' law says, a buoyant force begins to act on a body that is immersed in a liquid. Its value is equal to the weight of the water displaced by the body during immersion. The body cannot drown if the force of Archimedes is greater than or equal to the weight of the body. For this reason, the ship remains afloat.
The larger the volume of the body, the more water it displaces. An iron ball dropped into the water will immediately drown. But if you roll it out to the state of a thin sheet and make a ball out of it hollow inside, then such a volumetric structure will stay on the water, only slightly immersed in it.
Metal-skinned vessels are built in such a way that, at the time of submersion, the hull displaces a very large amount of water. Inside the ship's hull, there are many empty areas filled with air. Therefore, the average density of the vessel turns out to be much less than the density of the liquid.
How to keep the boat buoyant?
A ship is kept afloat as long as its skin is intact and undamaged. But the fate of the ship will be in jeopardy, should he get a hole. Water begins to flow through the hole in the skin inside the vessel, filling its internal cavities. And then the ship may well sink.
To preserve the buoyancy of the vessel upon receiving a hole, its internal space was divided by partitions. Then a small hole in one of the compartments did not threaten the general survivability of the vessel. Water was pumped out of the compartment, which was flooded, with the help of pumps, and they tried to close the hole.
Worse if several compartments were damaged at once. In this case, the ship could sink due to loss of balance.
At the beginning of the 20th century, Professor Krylov proposed deliberately flooding the compartments located in the part of the ship that is opposite to the cavities that were flooded. At the same time, the ship was somewhat upset in the water, but remained in a horizontal position and could not sink as a result of the rollover.
The proposal of the marine engineer was so unusual that it was ignored for a long time. Only after the defeat of the Russian fleet in the war with Japan was his idea adopted.