IGCSE 0625 · MECHANICS · 1.8

Pressure

Pressure as force per unit area, the Extended idea of pressure beneath a liquid, hydraulics, and how pressure connects to gas behaviour and the weather. It builds on forces and density.

TOPIC 1.8: PRESSURE CAMBRIDGE IGCSE PHYSICS 0625 · PATHWAYS TheLucidSTEM · thelucidstem.com BUILDS ON 1.5 Forces 1.4 Density LEADS TO 2.1 Gas pressure Hydraulics & weather PRESSURE & FLUIDS 1 · WHAT IS PRESSURE Pressure is the force acting on each unit of area. p = F / A unit: pascal (Pa) 1 Pa = 1 N/m² The same force on a small area gives a high pressure: that is why a sharp knife cuts. 2 · PRESSURE IN A LIQUID EXTENDED Pressure rises with depth and with the density of the liquid. Δp = ρ g Δh It pushes equally in all directions at a point. deeper water, stronger jet 3 · USING PRESSURE A liquid passes pressure on, so a small force can be turned into a large one. small F large F Hydraulic brakes and lifts use this force multiplying. 4 · PRESSURE CONNECTS TOPICS Gas pressure comes from particles hitting the walls of their container (Topic 2.1). A barometer measures atmospheric pressure; a manometer measures gas pressure. Differences in air pressure drive the weather. Whether an object floats depends on the upward pressure of the fluid around it.
TOPIC 1.8: PRESSURE CAMBRIDGE IGCSE PHYSICS 0625 · PATHWAYS TheLucidSTEM · thelucidstem.com BUILDS ON 1.5 Forces 1.4 Density LEADS TO 2.1 Gas pressure Hydraulics & weather PRESSURE & FLUIDS 1 · WHAT IS PRESSURE Pressure is the force acting on each unit of area. p = F / A unit: pascal (Pa) 1 Pa = 1 N/m² The same force on a small area gives a high pressure: that is why a sharp knife cuts. 2 · PRESSURE IN A LIQUID EXTENDED Pressure rises with depth and with the density of the liquid. Δp = ρ g Δh It pushes equally in all directions at a point. deeper water, stronger jet 3 · USING PRESSURE A liquid passes pressure on, so a small force can be turned into a large one. small F large F Hydraulic brakes and lifts use this force multiplying. 4 · PRESSURE CONNECTS TOPICS Gas pressure comes from particles hitting the walls of their container (Topic 2.1). A barometer measures atmospheric pressure; a manometer measures gas pressure. Differences in air pressure drive the weather. Whether an object floats depends on the upward pressure of the fluid around it.
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