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Buoyancy (/ ˈ b ɔɪ ən s i, ˈ b uː j ən s i /), [1] [2] or upthrust is a net upward force exerted by a fluid that opposes the weight of a partially or fully immersed object. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid.
An object whose weight exceeds its buoyancy tends to sink. Calculation of the upwards force on a submerged object during its accelerating period cannot be done by the Archimedes principle alone; it is necessary to consider dynamics of an object involving buoyancy. Once it fully sinks to the floor of the fluid or rises to the surface and settles ...
When the buoyancy effects are taken into account, an object falling through a fluid under its own weight can reach a terminal velocity (settling velocity) if the net force acting on the object becomes zero. When the terminal velocity is reached the weight of the object is exactly balanced by the upward buoyancy force and drag force. That is
An object immersed in a liquid displaces an amount of fluid equal to the object's volume. Thus, buoyancy is expressed through Archimedes' principle, which states that the weight of the object is reduced by its volume multiplied by the density of the fluid. If the weight of the object is less than this displaced quantity, the object floats; if ...
A fluid flowing around the surface of a solid object applies a force on it. It does not matter whether the object is moving through a stationary fluid (e.g. an aircraft flying through the air) or whether the object is stationary and the fluid is moving (e.g. a wing in a wind tunnel) or whether both are moving (e.g. a sailboat using the wind to ...
Neutral buoyancy occurs when an object's average density is equal to the density of the fluid in which it is immersed, resulting in the buoyant force balancing the force of gravity that would otherwise cause the object to sink (if the body's density is greater than the density of the fluid in which it is immersed) or rise (if it is less).
Normally, the effect of air buoyancy on objects of normal density is too small to be of any consequence in day-to-day activities. For instance, buoyancy's diminishing effect upon one's body weight (a relatively low-density object) is 1 ⁄ 860 that of gravity (for pure water it is about 1 ⁄ 770 that of gravity).
Diagram of how a Buoyancy Engine works. A buoyancy engine is a device that alters the buoyancy of a vehicle or object in order to either move it vertically, as in the case of underwater profiling floats and stealth buoys, or provide forward motion (therefore providing variable-buoyancy propulsion) such as with underwater gliders and some autonomous aircraft.