Why does an object float or sink when placed on the surface of water?
As an object comes in contact with the surface of a fluid it experiences two types of forces: gravitational force or gravity that pulls the object in downward direction and the second force is the force of buoyancy that pushes the object in upward direction. It is these two forces that are responsible for an object to float or sink i.e. if gravity >buoyancy then object sinks if gravity<buoyancy then object floats.
