Which of the following is the equation of a spherical ball of radius r, settling under gravity through a fluid, if acceleration due to gravity is considered as 10 m/s2?

• A. u = 4x ( sqrt { frac {5 times r times ( P )}{3 times Cd times }} )
• B. u = 4x ( sqrt { frac {r times ( P )}{Cd times }} )
• C. u = 5x ( sqrt { frac {5 times ( P )}{3 times Cd times }} )
• D. u = ( sqrt { frac {8 times ( P )}{3 times Cd times }} )