Answer
$\mathrm{a}.$ equal
$\mathrm{b}.$ No.
Work Step by Step
Archimedes' Principle
An object completely immersed in a fluid experiences an upward buoyant force equal in magnitude to the weight of fluid displaced by the object.
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$\mathrm{a}.$
The two spheres have the same volume, so they they displace the same volume (weight) of fluid. An equal buoyant force acts on each of them.
$\mathrm{b}.$
The magnitude of the buoyant force depends on the weight (and hence density) of a particular fluid. However, whatever the fluid is, the same volume is displaced by both spheres in part(a), so the answer to part (a) will be the same, whatever the fluid.
