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? V_{A}=0 V_{B}(inlet of the tube) = V_{E}, i think so because the diameter of the tube is constant. And the velocity through the tube all are constant. or V_{B}(inlet of the tube) = 0? but it could be right? Which point has the lowest pressure? should be P_{C} or P_{E}? Are the pressure of P_{B} and P_{E} the same? Is the P_{D} = 0? will all the pressure be different value if the fluid in a stationary motion? thanks all.