A vessel with water is placed on a weighing pan and reads 600 g. Now a ball of 40 g and density 0.80 g/cc is sunk into the water with a pin as shown in fig. keeping it sunk. The weighing pan will show a reading

Upthrust on ball = weight of displaced water  = V σg = (mρ)σ g = 400.8×1×g = 50 gAs the ball is sunk into the water with a pin by applying downward force equal to upthrust on it.So reading of weighing pan= weight of water + downward force against upthrust= 600 + 50 = 650 gm