ABSTRACT
Mating Newton’s laws with physical insight gave birth to the NavierStokes equation. One starts with the briefest possible summary of classical physics.
For fluids, the acceleration a→is that of a small region of the fluid (air or water). The mass m becomes the fluid density r (mass/volume) multiplied by the small volume of fluid. There are two forces; one is produced by pressure changes and the other is associated with friction or viscosity. The viscous force appears when regions of fluid slide past each other.
