Flotation

Buoyant Force : When a body immersed partly or wholly in a liquid, a force acts a on the body by the liquid in the upward direction. This force is called Buoyant force or force of buoyancy or upthrust. It is equal to the weight of liquid displayed by the body and acts at the centre of gravity of displayed liquid. Its study was first made by Archimedes.

Archimedes Principle : When a body is immersed partly or wholly in a liquid, there is an apparent loss in the weight of the body which is equal to the weight of liquid displayed by the body.

Law of Floatation :

A body float in a liquid if
(i) density of material of body is less than or equal to the density of liquid.

(ii) if density of material of body is equal to density of liquid, the body floats fully submerged in liquid in neutral equilibrium.

(iii) when body floats in neutral equilibrium, the weight of the body is equal to the weight of displayed liquid.

(iv) the centre of gravity of the body and the centre of gravity of the displayed liquid should be in one vertical line.

Centre of gravity of the liquid displayed by a body is called centre of buoyancy.

Meta Centre : When a floating body is slightly tilted from equilibrium position, the centre of buoyancy shifts. The point at which the vertical line line passing through the new position of centre of buoyancy meets with the initial line is called meta centre.