Answer
$8.63\;m/s^2$
Work Step by Step
If the sphere is free to move downward, the downward net forece is
$F_{net}=mg-F_b$
Let $a$ be the magnitude of the acceleration of the sphere.
Applying the Newton's second law of motion
$ma=mg-\rho gV$
or, $a=\frac{8.60\times9.81-1025\times9.81\times (\frac{4\times\pi \times 0.0622^3}{3})}{8.60}$
or, $\boxed{a=8.63\;m/s^2}$
