Water flows from a storage tank, over two triangular weirs, and into two irrigation chan...

Water flows from a storage tank, over two triangular weirs, and into two irrigation channels as shown in Video V10.13 and Fig. P10.71. The head for each weir is 0.4 ft, and the flowrate in the channel fed by the 90° V-notch weir is to be twice the flowrate in the other channel. Determine the angle θ for the second weir.