Pressure
Definition
Pressure is the amount of force exerted per unit area on a surface. It tells us how concentrated a force is — whether it’s spread out or focused on a small point.
Formula:
Pressure = Force /Area
Force (F) is measured in Newtons (N).
Area (A) is measured in square meters (m²).
Pressure (P) is measured in Pascals (Pa), where
1 Pa = 1 N/m².
Explanation
When the same force acts on a smaller area, pressure increases.
When the same force acts on a larger area, pressure decreases.
That’s why a knife with a sharp edge cuts better — the force is concentrated on a smaller area, producing higher pressure.
Types of Pressure
Atmospheric Pressure – The pressure exerted by the air around us.
At sea level, it is about 101,325 Pa or 1 atmosphere (1 atm).
Liquid Pressure – The pressure exerted by liquids due to their weight.
It increases with depth and density of the liquid.
Gas Pressure – Pressure exerted by gas particles when they collide with the walls of their container.
Blood Pressure – The force of blood pushing against the walls of blood vessels inside the human body.
Everyday Examples
Syringes use pressure to push medicine into the body.
Suction cups stick to surfaces because of pressure differences.
Hydraulic systems (like brakes in cars) use liquid pressure to multiply force.
Airplanes are designed to handle changes in air pressure at high altitudes.
Important Facts
Pressure in liquids acts in all directions.
Pressure increases with depth because the weight of the liquid above adds more force.
Instruments like barometers and manometers are used to measure pressure.