Introduction to Pressure

Pressure refers to the amount of force applied per unit area. It is a scalar quantity, which means it only has magnitude and no direction.
In physics, pressure is denoted by the letter P and is measured in pascals (Pa), where one pascal is equal to a force of one newton per square metre.
It can be calculated using the formula Pressure = Force / Area.

Factors Affecting Pressure

The amount of pressure an object experiences can be influenced by a variety of factors including the force applied and the surface area over which the force is distributed.
For a given force, if the area over which it is applied is reduced, the pressure increases. Conversely, if the area is increased, the pressure decreases.
This principle explains why a sharp knife cuts better than a blunt one: a smaller surface area means the force of your hand is concentrated over a smaller area, resulting in a higher pressure.

Pressure in fluids, which include both liquids and gases, increases with depth due to the weight of the fluid above pushing down.
A fluid at rest exerts pressure equally in all directions. This is known as Pascal’s Principle.
The pressure in a fluid at a certain depth or height can be found using the equation Pressure = Height x Density x Gravitational Field Strength.
This explains why divers experience more pressure the deeper they dive, and why your ears may pop on a plane or at high altitudes, due to changes in air pressure.

Atmospheric pressure is the pressure exerted by the weight of air in the Earth’s atmosphere. At sea level, the average atmospheric pressure is approximately 101,325 pascals.
Atmospheric pressure decreases with increasing altitude. This is why mountain climbers need to carry oxygen tanks – there is less air (and thus less oxygen) pressing down at higher altitudes.

In gases and fluids, pressure and volume are inversely related. This relationship is described by Boyle’s Law, which states that for a given amount of gas at a constant temperature, the product of volume and pressure is a constant.
Changing the pressure on a substance can sometimes change its state. For example, increasing pressure on a gas can compress it into a liquid, and reducing pressure on a liquid can allow it to evaporate into a gas.