A circular pipe has a fall of 4m and narrows so that, at exit, its area is one quarter that at inlet. The pressure at inlet is 20kN/m^2 above atmospheric and at exit, where the velocity is 15m/s, the pressure is atmospheric. Calculate the inlet velocity and mass flow rate of water through the pipe per unit cross-sectional area at inlet. Relevant Equations: Bernoullis I've got this so far (if it is correct!): 4 + (20 x 10³)/10³ x g + V²/2g = 15²/2g + h I'm not sure how to use the area values given to find out the velocity .. I presume I need to use Q = AV?