Pressure is defined as the physical force exerted on an object. The force applied is perpendicular to the surface of objects per unit area. The basic formula for pressure is F/A (Force per unit area). Unit of pressure is Pascals (Pa). Types of Pressures are Absolute, Atmospheric, Differential, and Gauge Pressure. While sipping beverages from a straw, have you noticed that you actually suck the air out of the straw? While you sip the beverage, you’re actually applying ‘Pressure’. But, what does it mean? Let’s study more about it.
What is Pressure?
The amount of force exerted (thrust) on a surface per unit area is defined as ‘Pressure’. It can also be defined as the ratio of the force to the area (over which the force is acting).

Formula and Unit of Pressure
Pressure (P) = Thrust/ Area

The SI unit is ‘pascals (Pa)’. 1 Pa = 1N/m2

Example: It is easier to hammer a sharp pin than to hammer a blunt pin. This is because the area at the end of the sharp pin is smaller than the area at the end of a blunt pin. This leads to an increase in pressure leading to hammer the sharp pin easily.

Types of Pressure
Atmospheric Pressure
Absolute Pressure
Differential Pressure
Gauge Pressure
Atmospheric Pressure
The earth’s atmospheric air is surrounded by a layer of gases and so this air surrounding the earth exerts a pressure known as the ‘atmospheric pressure’. Its value at sea level is 101325 Pa.

It is measured using a mercury barometer (hence atmospheric pressure is also known as barometric pressure), indicating the height of a column of mercury which exactly balances the weight of the column of atmosphere over the barometer. It can be expressed in several different systems of units such as millimeters (or inches) of mercury, pounds per square inch (psi), dynes per square centimeter, millibars (mb), standard atmospheres, or kilopascals.

The atmospheric pressure decreases near Earth’s surface, with height at a rate of about 3.5 millibars for every 30 meters (100 feet).

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