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I don't actually know the answer to this question. Let's say that you put a
solid object (a rock) in water and measured its effective weight*. Then,
you heat up the water. Will the effective weight decrease by a proportion
equal to the ratio of the before and after temperatures (or the square
thereof bc of the relationship between temperature and molecular velocity)?
If it is the pressure of the water molecules colliding with the object that
cause the buoyant force, then the answer should be "yes." But gut instinct
tells me that the answer is "no."
I cannot justify the discrepancy in my thought experiment and have never
tried the experiment. In fact, since the mass of water displaced would be
less (due to the decreased density of the water at higher temperatures), I
would expect that the effective weight of the rock might increase slightly.
This seems to contradict the molecular collision model. What am I missing?
Is my thought experiment all wrong?
In fact, since the mass of water displaced would be
less (due to the decreased density of the water at higher temperatures), I
would expect that the effective weight of the rock might increase slightly.
* I just made up the term "effective weight" to mean "weight as measured
when the object is under water" to simplify the discussion.