There's one answer available for this question on yahoo, but it's wrong. The textbook answer is 8.1 x 10^2 Newtons but I can't figure out how to get to that answer.
A spherical navigation buoy is tethered to the lake floor by a vertical cable. The outside diameter of the buoy is 1.00 m. The interior of the buoy consists of an aluminum shell 1.0 cm thick and the rest is solid plastic. The density of aluminum is 2700 kg/m^3 and the density of the plastic is 200 kg/m^3. The buoy is set to float exactly halfway out of the water. Determine the tension in the cable.
A spherical navigation buoy is tethered to the lake floor by a vertical cable. The outside diameter of the buoy is 1.00 m. The interior of the buoy consists of an aluminum shell 1.0 cm thick and the rest is solid plastic. The density of aluminum is 2700 kg/m^3 and the density of the plastic is 200 kg/m^3. The buoy is set to float exactly halfway out of the water. Determine the tension in the cable.