1. The problem statement, all variables and given/known data Let's say the surface of the fluid is very big as compare to the tube diameter. Are my assumptions below correct? VA=0 VB(inlet of the tube) = VE, i think so because the diameter of the tube is constant. And the velocity through the tube all are constant. or VB(inlet of the tube) = 0? but it could be right? Which point has the lowest pressure? should be PC or PE? Are the pressure of PB and PE the same? Is the PD = 0? will all the pressure be different value if the fluid in a stationary motion? thanks all.