Pressure in Fluids

This lesson covers pressure, including pressure in solids and fluids (liquids and gases), upthrust and atmospheric pressure — as required by the Edexcel GCSE Physics specification (1PH0), Topic 2: Motion and Forces. You need to know the equations for pressure, understand how pressure varies with depth, and explain floating and sinking.

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What Is Pressure?

Pressure is the force applied per unit area. It describes how concentrated a force is — the smaller the area, the greater the pressure for the same force.

Pressure = Force ÷ Area

P = F / A

Quantity	Symbol	Unit
Pressure	P	Pascals (Pa)
Force	F	Newtons (N)
Area	A	Square metres (m²)

1 Pa = 1 N/m² — a pressure of one pascal means a force of one newton is spread over one square metre.

Rearranging the Equation

• F = P × A (to find force)
• A = F ÷ P (to find area)