Question

How do submarines sink and float on water?

Answer 1

A submarine contains two different tanks in it. The outer tank is the reason behind the sinking and floating mechanisms of the submarine. Submarine stays afloat because the weight of water that it displaces equals the weight of the submarine. As gravity pulls down the submarine, water creates an opposite upward force called buoyant force which prevents the ship from sinking.

Complete answer:
Submarines contain tanks called ballast and trim tanks. These ballast and trim tanks are filled with water and air accordingly for the submarine to sink or float in water. When the submarine is floating on the surface, the tanks are filled with air so that the density of the submarine is reduced compared to that of the surrounding water. When the submarine dives, the tanks are flooded with water causing the density of the submarine to be greater than the surrounding water which makes the submarine sink easily.

Additional information:
Some submarines use two nulls-one inside the other- instead of ballast tanks. This design helps the submarine to allow the flood to outer hull with water, which results in sinking of the e submarine while the crew members and others live and work in the inner one. Best example for two nulls submarines is Russian alfa class submarine which is known for its incredible speed. It is still the fastest of its kind till today.

Note:
Many submarine explosions because of the compression of air. The air is compressed in the submarine so quickly that it would ignite before water reaches into the nulls, just like a diesel engine cylinder. The sudden acceleration of air molecules produces a shockwave that is similar to an explosion, disintegrating everyone inside instantly.