|MadSci Network: Physics|
Great question! You are right that the key principle involved here is buoyancy. Anytime we submerge an object under water, it displaces a certain amount of the water. For example, if we place a bowling ball in a swimming pool, the ball pushes aside an amount of water equal to its volume. Newton’s Law tells us that the water subsequently “pushes back” with a force equal to the weight of the displaced water. This force is what we call the buoyant force, and equals the weight of the displaced water. Therefore, whether or not an object sinks depends entirely on whether the object’s weight is greater than its buoyant force. %
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