February 2025 | Issue 775 | Page(s) 30 - 31 | John Watkinson
The number of molecules of air in the vicinity of a vehicle is simply fantastic and it is not practical to attempt to follow them all or predict what they will do. Fortunately, it is not necessary either.
Most of the important things can be established using approximations that simplify calculations without introducing much error. The assumption that air pressure and density remain substantially constant as it flows around a vehicle is one such.
The huge number of collisions between air molecules and their high speed means that, left to its own devices, a volume of air will end up having constant temperature throughout and no net or macroscopic motion.
