Question

Can you explain why a further decrease in the elongation of the string was not observed when it fully immersed in water

Answer 1

You will find that the elongation of the string or the reading of the balance decreases as the stone is gradually lowered in the water. However, no further change is observed once the stone gets fully immersed in the water. ... As discussed earlier, this upward force exerted by water is known as the force of buoyancy.

There is an upward buoyant force acting on the stone which pushes it up, thereby decreasing the length of the string.

Please mark it as a brain list answer