Before dropping a big wooden log and a small iron nail into the village pond, Tara says the log…
Before dropping a big wooden log and a small iron nail into the village pond, Tara says the log will float and the nail will sink. Her cousin Advait says it will be the other way round — the log is far heavier than the nail, so the log will sink and the light little nail will float. Whose prediction will come true?
Who do you think is right? Pick one.
The answer: Tara is right, floating depends on the material, not just the weight
Why
Advait is using a rule that seems to work in daily life — a heavy stone sinks, a light leaf floats — so he expects heavier to always mean sinking. But the pond breaks his rule: an iron nail weighs only a few grams and still sinks, while a log weighing many kilograms floats. For a solid piece, what decides it is the material. A piece of iron is heavier than the same amount (the same size) of water, so it sinks however small it is; most wood is lighter than the same size of water, so it floats however big it is. Test: cut a small chip off the log — the chip floats too; drop in an iron bolt ten times bigger than the nail — it still sinks. The size changed, the result didn't, because the material didn't. Tara is right: whether a solid floats depends on what it is made of, compared with the same amount of water, not on its weight alone.
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