Can 1 kg of Iron Float on Water? (Journal Article)

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Abstract: All general physics textbooks include a chapter regarding hydrostatics. Archimedes’ and Pascal’s principles are commonly covered, but surface tension is merely named. Few people knows that surface tension contributes to the buoyancy of any object, with more or less relevance.1 I think that including surface tension in general physics courses is important to understand all phenomena regarding hydrostatics, and this is why every year, before starting the lesson regarding hydrostatics, I pose a question to the students: Can 1 kg of iron float on water? Usually, some of them answer instinctively, saying, “no, that is not possible.” Others, knowing that I am used to showing them physics “tricks” in the classroom, remain thoughtful. Anyway, it is a question that would be answered negatively by around 90% of questioned people. However, as I will show, there are at least two ways to make 1 kg of iron float. When we think about 1 kg of iron or other metal, we often think about it as a compact cubic-shaped block. In that case, the answer is no, since the weight overcomes the other forces, such as the buoyancy force, among others.