Puzzles/Physics puzzles/A boat, a pool, and a lead ball/Solution
The water's level will be higher when the ball is in the boat.
When the ball is in the boat, it displaces the volume of water that weighs the same as the ball (see buoyancy). When the ball is in the water, it only displaces as much water as its volume.
For example, assume the ball's volume is 1.000 cubic metre. Then its mass is 11340 kg, and when placed in the boat it displaces 11340kg of water, which is the same as 11.340 cubic metres. When the ball is in the water, it onl displaces its own volume, which equals 1.000 cubic metre.
More water is displaced when the ball is in the boat, and so the water level rises more, leading to our result.