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What is the principle of floatation?

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Hint: To solve this question, we will be using Archimedes principle which states that if an object is partially or fully submerged in fluid, it exerts an upward force called buoyant force. The apparent decrease of weight caused by the buoyant force is equal to the weight of the fluid, displaced by the object. From the relation between actual weight and apparent weight, we will define the principle of floatation.

Complete step by step answer:
We know that, according to Archimedes' principle, the apparent decrease of an object’s weight is equal to the weight of the fluid displaced by the object when it is immersed in a fluid. We must know that the apparent weight in this case is the difference between original weight and the buoyant force excreted by the fluid. For floating of an object the actual weight is compensated by buoyant force.


Now, let us take ${{W}_{1}}=mg$ as the actual weight of the body and ${{W}_{2}}={{F}_{b}}$ as the buoyant force excreted by the fluid. Then,
If ${{W}_{1}}>{{W}_{2}}$, the resultant force on the object is downwards, causing it to sink. When the density of the object is greater than that of fluid, this condition arises.
If ${{W}_{1}}={{W}_{2}}$, when the densities of the object and the fluid are equal, the actual weight and the buoyant force become equal. The object can float at any depth in a fully submerged state.
And if ${{W}_{1}}<{{W}_{2}}$, the net force acts in the upward direction leading to a partially submerged condition of the object. The density of the object is less than the fluid in such cases.
So, we can conclude that floating of a body happens when the body and fluid are having the same densities and its weight is nullified by the buoyant force exerted by the fluid. The principle behind this is Archimedes' principle.

Note:
We must know that Archimedes principles have many more applications. The principle of floatation is mainly used for designing ships and submarines. It is also used in lactometers which is used for measuring purity of milk. Hydrometers used for measuring density of liquids also work on the basis of Archimedes principle.