1.8 Pressure
1.8 PRESSURE
Definitions
Pressure: Force acting per unit area.
Pascal (Pa): SI unit of pressure, equal to 1 N/m².
Atmospheric Pressure: Pressure exerted by the weight of the air above a surface.
Hydraulic System: A system where pressure is transmitted equally in all directions through a liquid.
Formulas
Pressure (p) = Force (F) / Area (A)
Pressure due to liquid: p = h × ρ × g
Force = Pressure × Area
Hydraulic systems: F / A = f / a
Key Notes
Pressure increases with depth in a liquid.
Liquids are incompressible, so pressure is transmitted equally.
Used in hydraulic lifts, brakes, and syringes.
Worked Examples
Pressure Calculation Force = 200 N, Area = 0.5 m² p = F / A = 200 / 0.5 = 400 Pa
Pressure in a Liquid h = 2 m, ρ = 1000 kg/m³, g = 9.8 m/s² p = h × ρ × g = 2 × 1000 × 9.8 = 19600 Pa
Hydraulic System Small piston: a = 0.01 m², f = 50 N Large piston: A = 0.5 m² F / A = f / a → 50 / 0.01 = F / 0.5 → F = 2500 N
Made by Hiba Shakeel
Curated by Yassein