It is a matter of buoyancy. There are large tanks that can be filled with sea water or with air. To submerge they pump the air into compressed tanks and the water fills it up sinking the sub. When they want to go back up, they blow the water out using the compressed air.
A submarine sinks as it fills its' ballast tanks with water. Then it uses pressurized air to empty them and float again.
It is when the object neither sinks nor conpleatly floats on top of the surface it stays in the middle kind of what a submarine does
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.
sinks
To control its buoyancy, the submarine has ballast tanksand auxiliary, or trim tanks, that can be alternately filled with water or air. When you fill it with water, it sinks, When you first let the water out then you let the air in (from compressed air in the submarine) it floats.
It is impossible to tell; whether an object floats or sinks depends on its density, not on its weight.
Not Yassine JR
Styrofoam floats on water, Soap sinks.
The Density.
This displacement of water creates an upward force called the buoyant force and acts opposite to gravity, which would pull the ship down. Unlike a ship, a submarine can control its buoyancy, thus allowing it to sink and surface at will.
A submarine floats and sinks by adjusting its buoyancy through the use of ballast tanks. When the submarine wants to sink, it fills these tanks with water, increasing its weight and causing it to descend. To float, the submarine expels the water from the ballast tanks, replacing it with air, which decreases its weight and allows it to rise. This ability to control buoyancy enables submarines to navigate at various depths in the water.
Iron has a higher density than water, so it sinks in water; but is less dense than mercury so it floats.