Question

Explain briefly how a submarine uses the principle of floatation

1. to float in the sea,
2. to lower itself and remain much below the surface and
3. to rise again to the surface.

Answer 1

1. Submarines works on Archimedes' principle.
2. A submarine sinks by taking water into its buoyancy tanks. Once submerged, the upthrust is unchanged but the weight of the submarine increases with the inflow of water and it sinks faster.
3. Each submarine is provided with ballast tanks. If the submarine has to submerge these tanks are filled with water. This makes the average density of the submarine greater than that of water as a result it sinks.
4. When the submarine has to be surfaced, compressed air is blown into these tanks to expel the water.
5. When the submarine has to be surfaced, compressed air is blown into these tanks to expel the water.
6. Again, the average density of the submarine becomes less than that of water, hence it floats.