Question

Water flowing along an open channel drives an undershot waterwheel of radius 2 m (figure). The water approaches the wheel with a speed of 5.0 m/s and leaves with a speed of 2.5 m/s; the amount of water passing by is 200 kg per second. At what rate does the water deliver angular momentum to the wheel (in kJ)? ___

Answer 1

$\frac{dL}{dt}=\frac{dm}{dt}(v_1-v_2)R=200\times (5-2.5)\times 2$
= 1000 J