# Buoyancy

Written by Jerry Ratzlaff on . Posted in Fluid Dynamics

Buoyancy, abbreviated as B, is when a liquid applies upward force on an object that is completely submerged or floating.

## Buoyancy Types

• Positive buoyancy  -  when the liquid force is greater than the object weight displacement.
• Negative buoyancy  -  when the liquid force is less than the object weight displacement.
• Neutral buoyancy  -  when the liquid force is equal to the object weight displace

## Buoyancy formula

$$\large{ B = \rho\; g \; V }$$
Symbol English Metric
$$\large{ B }$$ = buoyancy force $$\large{ lbf }$$  $$\large{N}$$
$$\large{ V }$$ = displaced volume $$\large{ ft^3 }$$ $$\large{ m^3 }$$
$$\large{ \rho }$$ (Gtrrk symbol rho) = fluid density $$\large{\frac{lbm}{ft^3}}$$ $$\large{\frac{kg}{m^3}}$$
$$\large{ g }$$ = gravitational acceleration  $$\large{\frac{ft}{sec^2}}$$    $$\large{\frac{m}{s^2}}$$

## Buoyancy formula

$$\large{ B = \rho \;g \;h\; A }$$
Symbol English Metric
$$\large{ B }$$ = buoyancy force $$\large{ lbf }$$  $$\large{N}$$
$$\large{ \rho }$$ (Gtrrk symbol rho) = fluid density $$\large{\frac{lbm}{ft^3}}$$ $$\large{\frac{kg}{m^3}}$$
$$\large{ g }$$ = gravitational acceleration  $$\large{\frac{ft}{sec^2}}$$    $$\large{\frac{m}{s^2}}$$
$$\large{ h }$$ = height of liquid displaced by a floating object $$\large{ ft }$$  $$\large{ m }$$
$$\large{ A }$$ = surface area of object  $$\large{ ft^2 }$$ $$\large{ m^2 }$$