Imagine a buoy made of cork floating on water. Assume that the buoy has a volume of 2 cubic feet (ft-cubed) and a density of 15 pounds per ft-cubed. Calculate the weight of the buoy as follows: 2 ft-cubed x 15 pounds / ft-cubed = 30 pounds.
Calculate the weight of water that has a volume equal to that of the buoy, using 62.4 pounds / ft-cubed as the density of water, as follows: 2 ft-cubed x 62.4 lbs / ft-cubed = 124.8 pounds / ft-cubed.
Note that the buoy, if held under water, displaces 124.8 pounds of water. According to Archimedes' principle, the buoyant force acting on the cork is 124.8 pounds, which is greater than the weight of the cork. Therefore, if the cork is released the buoyant force pushes it to the surface, where it remains partially immersed.
Calculate the volume of water displaced by the floating buoy, as follows: 30 pounds of water / [62.4 pounds / ft-cubed] = 0.481 ft-cubed.
Calculate the amount of the buoy's volume remaining above the surface of the water, as follows: 2 -- 0.481 = 1.519 ft-cubed.
The percentage of the buoy's volume above water is therefore: [1.519 / 2] x 100 = 76 percent.