SI Unit of Pressure

SI unit of pressure = Pascal (Pa)

Definition: 1 Pascal = 1 Newton per square metre 1 Pa = 1 N/m² = 1 kg/(m·s²)

Formula: P = F/A

Where: • P = pressure (Pa) • F = force applied (N) • A = area over which force is applied (m²)

Dimensional formula: [P] = [F]/[A] = [MLT⁻²]/[L²] = [ML⁻¹T⁻²]

The pascal is named after Blaise Pascal (1623–1662), French mathematician and physicist.

Unit → Symbol → Equivalent in Pa Pascal → Pa → 1 Pa Kilopascal → kPa → 1000 Pa Megapascal → MPa → 10⁶ Pa Atmosphere → atm → 101,325 Pa Bar → bar → 100,000 Pa mm of Hg (Torr) → Torr → 133.322 Pa Pounds per square inch → psi → 6894.76 Pa

Key values: • 1 atm = 101,325 Pa ≈ 101.3 kPa ≈ 1.013 bar • 1 bar = 10⁵ Pa (slightly less than 1 atm) • 1 atm = 760 mm Hg = 760 Torr • Normal blood pressure: ~120/80 mm Hg = ~16 kPa / ~10.7 kPa

Pressure in a fluid at depth h: P = P₀ + ρgh

Where: • P₀ = surface pressure (Pa) • ρ = density (kg/m³) • g = 9.8 m/s² • h = depth (m)

Atmospheric pressure: P₀ = 101,325 Pa (at sea level) Can also be measured by: P₀ = ρgh = 13600 × 9.8 × 0.76 = 101,293 Pa ≈ 101,325 Pa (mercury density × g × height of mercury column in barometer)

Pressure is a scalar quantity — it acts equally in all directions at any point in a fluid (Pascal's law).

Boyle's Law (at constant T): PV = constant (P and V are inversely proportional) P₁V₁ = P₂V₂