Problem 3: An impeller's inlet flow is purely axial. Its outlet radius is r = 0.6ft and its outlet vane thickness is b = 0.1ft. The net positive suction head at the impeller's inlet is NPSH = 100ft, the volumetric flow rate is 10ft/s and the suction specific speed is Nss = 6000. a) Find the rotational speed N, if we want to maintain a cavitation safety factor sf = 1.2 b) The impeller generates a pressure head increase AH = 50ft with a pumping efficiency np = 0.8. Find the outlet blade angle