Static pressure - Air molecules collide freely with a surface and each other.
Dynamic pressure - Air molecules are moved across the surface at speed and are therefore unable to strike the surface as much as they used to.
Total pressure - The same in both cases because we regard the air as an incompressible fluid (which is not true but is unimportant at low speeds).
Hope that helps.
Last edited by The500man; 23rd June 2012 at 10:25.