O **Archimedes' Theorem**, also called “**Archimedes' Principle**” (Law of Buoyancy) refers to the experience of the great Greek physicist-mathematician: Archimedes of Syracuse.

So, from the “gravity specific”, Archimedes' theorem allows us to calculate the value of the vertical and upward force (buoyancy force) that makes a body lighter inside a fluid.

Thus, the postulate of Archimedes says:

“

every body immersed in a fluid receives an upward thrust equal to the weight of the volume of the fluid displaced, for this reason, the bodies denser than water sink, while the less dense float”.

This explains why when we are immersed in water, whether at the beach or in the pool, the perception we have is that we are lighter in the water than outside of it, which explains the strength thrust (E) acting in the opposite direction to the weight force (P).

## Buoyancy

THE **buoyant force **(impulsion) is a force **hydrostatic** is **Vector greatness** (has module, direction and direction) represented by the letter F with an arrow above the letter.

The buoyant force designates the net force exerted by the fluid on a given body.

In the International System (SI) of Units, thrust is measured by the Newton unit (N). Thus, to calculate the buoyant force, the following formula is used:

**E= df. Vfd.g**

from where,

**df**: fluid density**Vfd**: fluid volume**g**: Acceleration of gravity

Thus, it is important to emphasize that if the density if the body is greater than the density of the fluid, the body will sink; if the density of the body is equivalent to the density of the fluid, the body will be in equilibrium with the fluid; and finally, if the density of the body is less than the density of the fluid, the body will float on the surface of the fluid.

In other words, if the buoyant force (E) is less than the weight force (P), the body will sink; if the buoyant force (E) has the same intensity as the weight force (P) the body will neither rise nor fall, remaining in balance; finally, if the buoyancy force is greater than the weight force (P), the body will rise to the surface.

Note that in the International System (SI) the **density** of fluid is measured in kilograms per cubic meter (**kg/m³**), O **volume** in cubic meters (**m³**) and the acceleration of gravity in meters per second squared (**m/s²**).

Read more:

- thrust formula
- Hydrostatics
- Hydrostatic Pressure
- Stevin's Theorem
- Pascal's Principle
- Physics Formulas
- Density exercises

## Curiosity

- The Dead Sea is a lake with a lot of salt, located in the Middle East and, therefore, has a very high density. Note that the greater the density of the fluid, the greater the acting buoyancy force; this explains why people have great facility to float in this place, since the acting buoyancy force has greater intensity than the weight force.

**Test your knowledge with questions about the topic in **Hydrostatic Exercises.