Buoyancy of a Floating Cylinder

A cylinder with diameter 2 m, length and volume is placed in a tub of liquid. Depending on the specific gravities of the cylinder and the liquid, the cylinder either floats or sinks. You can select the kind of cylinder and liquid with buttons or their specific gravities with sliders. The displaced liquid volume, the cylinder weight and the buoyant force are shown. If the cylinder floats, the distance from the top of the cylinder to the liquid surface is shown.
  • Contributed by: Neil Hendren
  • With additional contributions by: John L. Falconer
  • (University of Colorado Boulder, Department of Chemical and Biological Engineering)


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The buoyant force is equal to the weight of the liquid displaced by an object:
where is the buoyant force, is the density of the liquid, is gravitational acceleration, and are the specific weights of the liquid and water, respectively, and is the specific gravity of the liquid with respect to water.
At equilibrium, an object's buoyant force is equivalent to its weight, or gravitational force :
. (2)
Here, the subscript denotes the properties of the cylinder. If the specific weight of the object is less than the buoyant force acting upon it, it will float. Otherwise, it will sink.
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