# Buoyancy

It is a force exerted by water. The same force that keeps a person floating in the water also keeps a transatlantic floating in the sea. We call this force thrust.

So what keeps the bodies floating in the water is the buoyancy. But this force is also present when the object, denser than water, sinks. Or when, having the same density of water, the object is completely submerged, but in equilibrium.

## Archimedes Principle

"Every body immersed in a liquid receives from the liquid the action of thrust, which is a vertically directed force from the bottom up. The intensity of the thrust is equal to the weight of the volume of the displaced liquid."

Archimedes was a famous mathematician and inventor of various mechanical devices. He made important discoveries in geometry and mathematics.

## What floats and what sinks in water?

Not every body floats or sinks in water. Some maintain balance within the water. If the body floats, it is because this body is less dense than water. So the weight of the body is equal to the thrust, that is, the weight of the body is equal to the weight of the water flowing.

If the body sinks it is because this body is denser than water. So body weight is greater than thrust, that is, body weight is greater than the weight of the moving water flow.

If the body is in balance within the liquid, it is because the body has the same density as water. It neither sinks nor floats in water. It is completely immersed in water, without touching the bottom, maintaining balance.

## Water: Pressure

The main scientist who studied pressure in liquids was Blaise Pascal. He was French, was a mathematician, physicist, philosopher and writer. But before Pascal formulated his theories, other scientists studied the behavior of liquids.

### Water exerts pressure

When there is water in the containers, it exerts pressure on the walls (or inner surfaces) of the container. This force that acts in a certain area is called pressure:

P = F / A

P = pressure
F = force
A = area

### Pressure and Depth

What happens to a balloon, which is filled with water and is pierced at various points with a pin? If you perform this experiment, you will notice that the water jets coming out of the lower holes go farther than the jets in the upper holes. This is because water pressure increases as depth increases. This also explains why the dams are wider underneath.

Another example that demonstrates water pressure is diving. How are fish, submarines and people diving in the sea not overwhelmed by water pressure? What happens is that they can only dive to some depth, otherwise they can be crushed by the strong water pressure.

A body dipped in water should not only receive pressure from above, but from all sides. From the outside in and from the inside out (keeping the balance). The pressure exerted by a liquid does not depend on the shape of the container containing it, but only on the depth, or height, and the density of the liquid.

### Communicating vessels

It is the connection of two containers through a closed duct.

A container formed by several branches that communicate with each other constitutes a system of communicating vessels. Example: tube in U.

"A liquid placed in a system of intercommunicating vessels always has the same level in all vessels, regardless of the shape and diameter of these vessels."