# 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 displacement.

## Buoyancy formulas

 $$\large{ B = p \;A }$$ $$\large{ B = \rho\; V\; g }$$ $$\large{ B = \rho \;g \;h\; A }$$

### Where:

 Units 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 $$\large{\frac{ft}{sec^2}}$$ $$\large{\frac{m}{s^2}}$$ $$\large{ h }$$ = height of liquid displaced by a floating object $$\large{ ft }$$ $$\large{ m }$$ $$\large{ p }$$ = pressure $$\large{\frac{lbf}{in^2}}$$ $$\large{\frac{N}{m^2}}$$ $$\large{ A }$$ = surface area of object $$\large{ ft^2 }$$ $$\large{ m^2 }$$