Fundamental Physical Quantities of Aerodynamics (Flowing gas) The flow of air over the surface of an airplane is the basic source of the lifting or sustaining force that allows a heavier then air machine to fly the science that deals with the flow of air or gas is called aerodynamics four fundamental physical quantities in the language aerodynamics are pressure, density, temperature and velocity of flow PRESSURE 'P' Pressure is the normal force per unit area exerted on a surface due to the time rate of change of momentum of the gas molecules impacting on the surface p=F(normal) / a units of pressure N/m 2 , pascal , bar , atm , lb/ft 2 Some conversations 1 ft = 30.48 cm 1 kg =2,205 ponds ( Lb m ) 1 slug = 32.3 Lb m 1 mile = 1609.3 m = 1.609 km DENSITY " ρ " t he density of the substance is the mass of the substance per unit volume units of de...