Why does an object float or sink when placed on the surface of water ?

Solution:
If the density of an object is more than the density of the liquid, then it sinks in the liquid. This is because the buoyant force acting on the object is less than the weight of the object. If the density of the object is less than or equal to the density of the liquid, then it floats on the surface of the liquid. This is because the buoyant force acting on the object is equal to the weight of the object.