What is Bouyancy: Definition and 53 Discussions

Buoyancy (), or upthrust, is an 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. Thus the pressure at the bottom of a column of fluid is greater than at the top of the column. Similarly, the pressure at the bottom of an object submerged in a fluid is greater than at the top of the object. The pressure difference results in a net upward force on the object. The magnitude of the force is proportional to the pressure difference, and (as explained by Archimedes' principle) is equivalent to the weight of the fluid that would otherwise occupy the submerged volume of the object, i.e. the displaced fluid.
For this reason, an object whose average density is greater than that of the fluid in which it is submerged tends to sink. If the object is less dense than the liquid, the force can keep the object afloat. This can occur only in a non-inertial reference frame, which either has a gravitational field or is accelerating due to a force other than gravity defining a "downward" direction.Buoyancy also applies to fluid mixtures, and is the most common driving force of convection currents. In these cases, the mathematical modelling is altered to apply to continuua, but the principles remain the same. Examples of buoyancy driven flows include the spontaneous separation of air and water or oil and water.
The center of buoyancy of an object is the center of gravity of the displaced volume of fluid.

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  1. matthyaouw

    A bit of a basic question: bouyancy

    (This isn't a homework question before you ask- it just came up in something I was reading.) Am I right in thinking that a boat floating in water would float neither higher nor lower if the gravity were altered, as its mass would remain constant? Would the same remain true if an object were...
  2. B

    Identifying Material Density Using Buoyancy and Volume

    A solid object floats on ethyl alcohol, with 68.2% of the object’s volume submerged. Using Table 11.1, identify the substance from which the object is made. ethyl alcohol has mass density of 806 kg/m what is the other substances mass density
  3. A

    How does bouyancy work from a molecular point of view?

    Gas/liquid/solid in solid is irrelevant, liquid in gas is too dense to be bouyant, solid in liquid/gas and gas in liquid are easy. So I'm mostly interested in the liquid in liquid and gas in gas cases. Thanks.
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