Pressure is the physical quantity that measures the force exerted on a unit of surface applied in a direction perpendicular to it.

In everyday life we find many examples in which this concept appears that we often use: in meteorology, health, engineering, etc.

## Pressure Types

There are the following types:

Hydrostatic pressure: the pressure exerted by liquids that cannot be compressed on objects that are in contact with them.

Absolute pressure: is the sum of the force per unit area of a given system and that of the air that surrounds it.

Gauge pressure (also called relative pressure) is the difference between absolute (real) and atmospheric.

Atmospheric pressure: it is the force per unit area that the air exerts on the earth's surface. At sea level, 1 atm equals 101325 Pa.

Arterial or blood: when we refer to the force exerted by blood on the inner surface of the arteries.

Osmotic: it is the force exerted per unit area of a solution against a closed semi-permeable membrane.

## What Is the Unit of Pressure?

The unit of pressure in the International system of units is the pascal (Pa), in honor of Blaise Pascal. One pascal is the pressure exerted by a total force of one newton acting uniformly on one square meter (Pa = N / m2).

Pascal (Pa) is a small unit, and sometimes it is convenient to use other units of measurement:

Millimeter of mercury (mmHg) is a unit that is still used to measure pressure in medicine, meteorology, aviation and is equivalent to 133,322 387 415 Pa.

Pub. The use of this unit is accepted within the SI although it is not recommended. It is often used because it has a value very close to 1 atm. 1 bar = 100,000 Pa

Hectopascals (HPa). This unit is used in meteorology and is equivalent to 100 Pa.

Atmosphere (atm). The atmosphere is a unit that indicates the pressure that the earth's atmosphere produces on average at the earth's surface.

Kiloponds per square centimeter (kp / cm2). This unit is used in engineering. The kilopond is equal to the weight of a mass of one kilogram (9.8 N).

Pound of force per square inch (lbf / in²) is a unit that belongs to the Anglo-Saxon system. To refer to it, the acronym psi (pounds-force per square inch) are also used.