A common balance has a beaker of water and a piece of stone in one of the pans and is balanced. Now, the stone is dipped into the beaker of water. Is any change in reading of the balance observed?

Explanation

When the piece of stone is immersed in the water of the beaker, the balance beam remains in its equilibrium condition. Due to the upthrust exerted by water, the piece of stone loses a part of its weight. According to Newton.s third law of motion, the reaction of the upthrust of water will act vertically downwards on the pan of the common balance. As the apparent loss in weight of the piece of stone becomes equal to the downward reaction force on the balance pan, the net weight remains the same and hence the balance beam remains in its equilibrium condition.