Buoyancy is the force that causes objects to float. It is the force exerted on an object that is partly or wholly immersed in a fluid.
Principle of Buoyancy
The principle of buoyancy is called Archimedes’ Principle, as it was discovered by the Greek mathematician in the third century. The principle states that ‘The upward buoyant force that is exerted on a body immersed in a fluid, whether partially or fully submerged, is equal to the weight of the fluid that the body displaces and acts in the upward direction at the centre of mass of the displaced fluid”.
An object that is completely immersed in a fluid displaces a volume of fluid, exactly equal to the volume of the object. The buoyant force, or the weight of the volume of the displaced fluid, will depend on the density of the fluid as well as the displaced volume. The principle applies to all fluids including gases.