# Buoyancy

Buoyancy is defined as the tendency of a body to float or rise when submerged in a fluid. The resultant force acting on a submerged body by the fluid is called the * buoyant force * and can be expressed as

F = V γ

=V ρ g(1)

where

F = buoyant force (N)

V = body volume (m^{ 3 })

γ = ρ g = specific weight of fluid (N/m^{ 3 })

ρ= density of fluid (kg/m^{ 3 })

g= acceleration of gravity (= 9.81 m/s^{ 2 })

The buoyant force acts upwards.

Archimedes' principle indicates that

* "the upward buoyant force that is exerted on a body fully or partially submerged in a fluid - equals to the weight of the fluid that the body displaces" *

- if the body weighs more than the fluid - it sinks
- if the body weighs less than the fluid - it floats

### Example - Buoyant Force acting on a Floating Box

A plastic box with length * 0.3 m * and width * 0.4 m * is submerged * 0.1 m * into water. The water density is * 1000 kg/m * ^{ 3 } .

The buoyant force acting on the box can be calculated with * (1) *

* F = (0.3 m) (0.4 m) (0.1 m) ( 1000 kg/m ^{ 3 } ) ( 9.81 m/s ^{ 2 } ) *

* = 119 N *

## Related Topics

### • Fluid Mechanics

The study of fluids - liquids and gases. Involving velocity, pressure, density and temperature as functions of space and time.

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