Question

Should a given object be more buoyant in liquid mercury than in liquid water?

Answer 1

The answer is an emphatic `"YES"`.

Explanation:

Consider: (i) Archimedes principle, any object, wholly or partially immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object, and (ii) the density of mercury (`13.5*g*mL^-1`).

When a body floats in water, the body displaces a volume of water equal to the volume of the body. An upwards force results. On the other hand, mercury is a fluid much more dense than water (`10xx` more in fact).

Objects should therefore be much more buoyant in mercury, and indeed they are. (I remember a classic science fiction novel, which described swimmers floating on rocks in mercury pools on 1 of the moons of Jupiter.)