why does the object apparently lose its weight wen completely sbmerged in water?how is this made possible?

Answer 1

It's called 'bouyancy' and the apparent weight 'lost' is exactly equal to the weight of the fluid displaced. It happens because the net force acting at all points within a fluid is zero. That means that if you 'push' hard enough to displace 10 kg of fluid, the fluid 'pushes back' with exactly the same amount of force and the 'net force' acting on you is as if you had lost 10 kg of mass.

Doug

Answer 2

The pressure under water (or any liquid) increases with depth.
So if you immerse any object, the pressure on the bottom surface will exceed that on the upper surface.
The excess pressure will produce an upward force, called the upthrust, on the object which acts so as to reduce its weight partially.