How to Calculate Weight for Buoyancy
The buoyant force is what keeps boats and other floating objects from sinking. An object placed in water causes the water level to rise an amount equal to the volume of the object below the surface. Archimedes' principle states that the weight of the water moved by the presence of the object equals the buoyant force upward on the object. Once the volume of the submerged object is determined, the weight of the displaced water can be found using the weight density of water.
Other People Are Reading
Instructions
-
-
1
Measure the length, width and depth in inches of the part of the object submerged in the water. For example, the dimensions of the submerged portion of a raft might include a length of 100 inches, a width of 60 inches and a depth of 3 inches.
-
2
Convert the measurements to feet by dividing by 12. This step leads to a length of 8.3 feet, a width of 5 feet and a depth of 0.25 feet.
-
-
3
Multiply the length by the width by the depth to arrive at the volume of displaced water in cubic feet. Continuing the example, you have 8.3 feet times 5 feet times 0.25 feet, or a volume of 10.4 cubic feet.
-
4
Multiply the volume by the weight density of water to obtain the buoyant force applied to the object in pounds. The weight density of water equals 62.4 pounds per cubic foot. Completing the exercise yields 10.4 cubic feet times 62.4 pounds per cubic foot, which equals a buoyant force of 649.0 pounds.
-
1
Tips & Warnings
If the combined weight of the floating object plus its contents exceeds the buoyant force, the object will sink.
