Two spheres of identical volume are completely submerged in the same tank of fresh water and released from rest at the same depth. Sphere A is a solid steel ball. Sphere B is a thin-walled plastic shell filled with air. No other forces aside from those exerted by the water and gravity are significant.
(a) For each sphere, identify the direction of its initial acceleration just after release. Justify your answer by comparing the relevant forces.
(b) Explain why the magnitudes of the buoyant forces on the two spheres are equal even though their accelerations differ.
(c) Without performing numerical calculations, discuss which sphere (if either) will experience a change in the magnitude of its acceleration as it moves, assuming the water is still and viscous drag remains negligible.