Objects appear to be less heavy in water or in any liquid because the liquid or water exerts an upward force on the objects immersed in it. Thus the upward force acting on an object immersed in a liquid resulting in the apparent loss of weight of the object is called the buoyant force.The buoyant force experienced by a body when submerged in a liquid depends on the volume of the body and the density of the liquid.
Archimedes’ studied the upthrust acting on a body, when it is partially or completely immersed in a fluid by performing several experiments and then stated the following principle known as the Archimedes’ Principle.
Principle of Archimedes
It states that when a body is totally or partially immersed in a fluid it experiences an upthrust equal to the weight of the fluid displaced.
If the weight of the water displaced is less than the weight of the object, the object will sink. Otherwise the object will float, with the weight of the water displaced equal to the weight of the object.