I'm not sure what you mean, so your saying let Pout equal to Patm as there is no gauge pressure on exit?
My understanding is that if there is a gauge pressure on exit you would need to have been told that in order to calculate Pin
Homework Statement
Water flows through a circular pipe with a 180° horizontal elbow and exits to the atmosphere through a nozzle as shown in Fig. Q3. The diameter of the pipe is 300 mm and the diameter of the nozzle exit is 160 mm. The density of water is 999 kg/m3 . The mass flow rate of...