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Question
Explain why an iron needle sinks in water, but a ship made of iron floats on water.
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Solution
An iron needle is solid and the density of iron is more than that of water. The weight of the iron needle is more than the buoyant force of water on it, so it sinks in water. Although a ship is made of iron, it has hollow spaces that are filled with air, which makes its average density less than that of water, so the ship floats on water.
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