Aladdin's Magic ChessboardYoonjin LeeAward: Top 100
School: chadwick international In the photo, a chessboard floats on a pool, carrying several pieces across the water. However, a single chess piece has fallen into the water, sinking to the bottom. How come the entire chessboard with multiple pieces can float, while the singular chess piece, obviously much lighter than the entire board with many pieces on it, sinks? An object will float if the buoyant force, an upwards force acting on the object by the fluid, is equal in magnitude to the object's weight. But what determines the magnitude of the buoyant force? The Archimedes principle states that the buoyant force applied to an object is equal to the weight of the fluid displaced by the object. Therefore, objects that are denser than the fluid sink, because the weight of the fluid displaced by the object can never be greater than the weight of the object itself. On the other hand, objects that are lighter than the fluid would float. The chessboard in the photo is of a light material that is much less dense than water. Even if a few pieces are added, the weight of the fluid displaced can still be greater than the weight of the chessboard and the objects on top of it. However, the chess pieces are made of a material that is denser than water, which means that by itself, they will sink. This leads to a phenomenon like Aladdin's magic carpet, but in this case, it can be explained scientifically. 
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