I’m sitting in a boat in a pool. In the boat with me is a cannonball. What happens to the level of the pool if I take the cannonball out of the boat and drop it into the pool? Does the level increase, decrease or stay the same?
This puzzle uses Archimedes' principle: "The Buoyant force on an object submerged or floating is equal to the weight of the displaced liquid." They also use Newton's law: "The net force on a body in equilibrium is zero."
The cannonball in the boat adds to the boat's weight, and the presence of the cannonball there causes a displacement of an amount of water which weighs as much as the cannonball.
Or, in other words, the cannonball in the boat displaces a weight of water equal to its own WEIGHT. When the cannonball is at the bottom of the lake it displaces an amount of water equal to its own VOLUME. Its weight is greater than the weight of an equivalent volume of water (that's why it sank), so it displaces more water when in the boat than when at the bottom.
Therefore, the water level of the lake drops when the cannonball is thrown overboard.
Solution !!!!
