A rubber ball filled with air has a diameter of 21.7 cm and a mass of 0.523 kg. What force is required to hold the ball in equilibrium immediately below the surface of water in a swimming pool?
Let that required force be F.
F + M*g = (1/6) pi*D^3* 1000 kg/m^3*g
The term on the right is the buoyancy force.
Solve for F in Newtons.
g is the acceleration of gravity, 9.8 m.s^2
M = 0.523 kg
D = 0.217 m