(a) The upward force exerted by a liquid on the body, immersed in the liquid is known as the upthrust or buoyant force. Buoyant force acting on a body depends on the volume of the body submerged in the liquid and the density of the liquid in which the body is immersed.
(b) Archimedes determined the amount of buoyant force exerted by the liquid on the body. According to him, when a body is wholly or partially immersed in a liquid at rest, it experiences an upthrust, equal to the weight of the liquid displaced by the body.
(i) A body will sink in a liquid if its density is more than that of the liquid in which it is immersed.
(ii) The body floats being completely immersed in water if the density of the body is equal to the density of the liquid.
(iii) The body floats being partially immersed if the density of the body is less than the density of liquid