Hey... I have a question about what is causing the Bernoulli effect...a moving fluid (say water) will exert lower pressure on the walls of a container (say a pipe) than a stationary fluid will....and since the water molecules move about randomly... There seems to be only two possibilities: 1. The increase in velocity causes a decrease on the number of molecules in the pipe 2. The increase in velocity causes a decrease in the energy of the collisions between the water molecules and the walls of the pipe.... Number one doesn't make as much sense as #2, so I am assuming that #2 is correct... So how would a horizontal velocity increase affect the vertical collisions between the water and the pipe? What is happening to the water molecules to cause the decreased energy per collision with the pipe? Thanks.