SDN Members don't see this ad. (About Ads) Ok I know there's thousands of threads like this, but my physics prof skipped fluids, so will somebody tell me that I'm correct. Ok in a closed system only relate area w/ the velocity b/c flow rate is constant Q=av. Then I relate the velocity to the pressure w/ Bernoullis's. This is the typical thought process right? In an open system if P increased V can increase too, but in a closed system they're inversly related. Do I need to know anything else about Bernoulli's, like the v is squared? Or am I straight? Also, how do I know when to apply Poiseuille's law vs q=av?