[The Radium King]

bernoulli effect - pressure is related to velocity. think a wing; the air traveling over the longer curved upper surface has to travel faster than the air following the shorter straight bottom surface if all air is to get to the back of the wing at the same time. the faster air gets 'spread out' (same unit of air has to cover larger area) and if volume increases then pressure has to decrease (pv=nrt). lower pressure on upper surface of wing means wing rises.

so, higher speed = lower pressure. conversely, lower speed = higher pressure. relatively (again, pv=nrt and if volume is proportional to velocity then a decrease in v means an increase in p). wind tunnel images show slower air in the area in front of the rear wheel.