A rocket sled is to be slowed from an initial speed of 300 m=s by lowering a scoop into a water trough. The scoop is 0.3 m wide; it deflects the water through 150 . The trough is 800 m long. The mass of the sled is 8000 kg. At the initial speed it experiences an aerodynamic drag force of 90 kN. The aerodynamic force is proportional to the square of the sled speed. It is desired to slow the sled to 100 m=s. Determine the depth D to which the scoop must be lowered into the water.