Buoyancy

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The illustration of the buoyancy in question. In the object which floats on the surface of the water, and stands still, buoyancy (buoyancy) matches with gravity (gravity).

An illustration of the water pressure. I am proportional, and the water pressure becomes strong so that the depth of the water is deepened. The direction of the water pressure works in the aspect of the object to the vertical direction.

The buoyancy (ふりょく British: buoyancy) is power to act to an object of fluids such as the water in the direction where is reverse to the gravity.

The cause of the buoyancy is explained by Archimedes' principle. The object catches the pressure (resting hydraulic pressure) from a fluid. The pressure is different then under the top of the object (like atmospheric pressure of the top of Mount Fuji and the atmospheric pressure of the foot), and power to receive from the bottom is bigger. A difference of the power of the top and bottom that this object receives is buoyancy. In other words, the ascending power that is reverse to the downward gravity acts on an object.

Formulation

The buoyancy that an object catches is equal to the gravity to act on a fluid (the neighborhood) of the volume same as the object. In other words, I am as follows.

${\displaystyle F_{b}=\rho _{f}Vg}$ 

F_b ：Buoyancy (N, kg·m/s²)

ρ_f ：Density (kg/m³) of the fluid

V ：The volume of the object (m³)

g ：Acceleration of gravity (m/s²)

I use an emission theorem for the close derivation of this expression.

Furthermore, the resultant with gravity and the buoyancy to act on an object if the density of the object is ρ_s (by an upswing for plus),

${\displaystyle F=(\rho _{f}-\rho _{s})Vg}$ 

となる. Therefore

• Time, F where an object is lighter than a fluid (ρs <ρf) > 0 namely the object loosens
• An object is heavier than a fluid (ρ_s > At ρf) time, F <0 namely the object sinks

I understand a thing.

several no dimensions

It relates to buoyancy, and, in the number of no dimensions used with hydrodynamics, there is the following. All express the ratio of the size with some kind of other power.

• The ratio with number of Richardson - inertial force
• The ratio with the number of グラスホフ - viscosity power
• The ratio with the Reilly number - thermal diffusion
• The ratio with number of Eotvos - surface tension

Allied item

Wiki media Commons has a category in conjunction with the buoyancy.

• Archimedes' principle
• Liquefaction
• Ship
• Airship・Balloon・Balloon
• Lift

It is acquired by "https://ja.wikipedia.org/w/index.php?title= buoyancy &oldid=58959804"

This article is taken from the Japanese Wikipedia Buoyancy

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