Submarines: How They Work - Archimedes' Principle
Whether a submarine is floating or submerging depends on the ship's buoyancy. Buoyancy is controlled by the ballast
tanks, which are found between the submarine's inner and
A submarine resting on the surface has positive buoyancy,
which means it is less dense than the water around it and will float.
At this time, the ballast tanks are mainly full of air.
To submerge, the wsubmarine must have negative buoyancy.
Vents on top of the ballast tanks are opened. Seawater coming in
through the flood ports forces air
out the vents, and the submarine begins to sink.
The submarine ballast tanks now filled with seawater is denser than the
surrounding water. The exact depth can be controlled by adjusting
the water to air ratio in the ballast tanks. Submerged, the submarine
can obtain neutral buoyancy. That means the weight
of the submarine equals the amount of water it displaces. The submarine
will neither rise nor sink in this state.
To make the submarine rise again, compressed air is simply blown into
the tanks forcing the seawater out. The submarine gains positive
buoyancy, becomes less dense than the water and rises.