submarine and steamboat
Massive ballast tanks can be filled with water or air, changing the weight and buoyancy of a sub. Once dived a sub can use hydroplanes to angle it towards the surface and use propulsion to drive to the surface.
The submarine
Bangladesh has joined the consortium of SEA-ME-WE-4 submarine cable, which starts its commercial activities from 21st may, 2006.
The first underwater warship was developed by Leonardo da Vinci. da Vinci kept his plans secret because he didn't want to make war any more terrifying than it already was. In 1578 William Borne began drawing plans for a submarine. His submarine was never built. Borne's submarine worked by using extra tanks which could be filled so the submarine would submerge. The tanks would be emptied for the submarine to surface. In 1620 Cornelis Drebbel, a Dutch inventor, built a leather covered rowboat with oars. The oars came out through watertight seals. Twelve people could ride in the submarine. Drebbel was an engineer who worked for the British navy. Drebbel was the first to discuss the problem of air replenishment while the submarine submerged. Drebbel's submarine could only go down about fifteen feet. It could stay underwater for a couple of hours.
The submarine will float when its weight is equal to the upthrust acting on it. This is because the upthrust force pushing the submarine upwards is equal to the weight of the water displaced by the submarine, resulting in a state of equilibrium where the submarine neither sinks nor floats.
A submarine actually controls its weight by allowing water to enter or exit hollow chambers in its hull. These chambers are called ballast tanks. Ballast is anything carried in a ship to give stability. When water is allowed to flood into a submarine's ballast tanks, the weight of the submarine increases. When this increased weight exceeds the submarine's buoyancy, the submarine will sink. To allow the submarine to rise, air is pumped into the ballast tanks. The air forces out the water, reducing the weight of the submarine. The submarine then becomes lighter, buoyancy increases, and it floats to the surface. A submarine can also be made to "float" underwater at any depth by adjusting the amount of water weight in its ballast tanks.
The buoyancy force on a submerged submarine equals the weight of the water displaced by the submarine. This force acts in the opposite direction to the gravitational force, allowing the submarine to float or sink in the water.
I dont really get the question but a submarine?
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the weight of the ocean water displaced by the submarine.
25,000 tonnes
Submarines can pump sea water into or out of ballast tanks, if they wish to change their weight (of course, anything that enters or leaves a submarine will also change its weight - people, supplies, weapons, etc. - but if you just want to change the weight, the easiest way is to pump water into the submarine).
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The submarine's density decreases when water is pumped out of its floatation tank because the overall volume of the submarine remains the same while the mass decreases. This leads to a lower density, allowing the submarine to float.
This is not a "cut and dry" question. It depends on the pay grade and whether they are wearing their "dophins" or not. They cannot receive submarine pay until they finish the submarine qualifications and put on the submarine pin or "dolphins".
The apparent weight of the submarine is calculated by subtracting the weight of the water it displaces from its actual weight. In this case, the apparent weight of the submarine would be 1256N - 1562N = -306N. This negative value indicates that the submarine will feel lighter when submerged in water due to the buoyant force acting on it.