Buoyancy

Buoyancy is the force on a body immersed totally or partially in a fluid (liquid or gas) in a gravity field. Also referred to as Archimedes' principle and often stated as follows: "the upward buoyant force that is exerted on a body immersed in a fluid, whether fully or partially submerged, is equal to the weight of the fluid that the body displaces". "

Example of buoyancy

Diagram showing buoyancy.nbsp;© Wikipedia, public domain

Thus, if a cube is subjected to a force of gravity F_p and immersed in water, it will be subject to buoyancy F_A in in a direction opposite to this force of gravity. For the same volume but different densities of the cube, the force F_p will not be the same, but the force F_A will not change. The cube will float if F_A>F_p and sink if F_Ap.

Applications of buoyancy

Buoyancy thus explains why ships float and why balloons can rise in the air. It also explains how divers can control their buoyancy by inflating or deflating a buoyancy compensator.