Page:Aerial Flight - Volume 1 - Aerodynamics - Frederick Lanchester - 1906.djvu/89

Rh Stokes law is based on a system of motion of the fluid that has been mathematically investigated and the lines of flow plotted from an equation. It may be remarked that this system of motion can never exist in its entirety, for it involves an infinite



quantity of momentum and an infinite quantity of energy ; in other words, the steady state involves a force applied for an infinite time through an infinite distance; it also constitutes a violation of the principle of no momentum of § 5.

If we suppose that the stress, due to the propulsion or to the