How much air must be pushed downward at 60.0 m/s to keep an 800-kg helicopter aloft?
A) 131 kg/s
B) 196 kg/s
C) 294 kg/s
D) 392 kg/s

Question

Quizplus · Accepted Answer

The force required to keep the helicopter aloft is equal to its weight, which is 800 kg * 9.8 m/s^2 = 7840 N. The air must exert an upward force of 7840 N on the helicopter, which means that it must push downward with an equal and opposite force of 7840 N. The mass flow rate of the air is then 7840 N / (60.0 m/s) = 131 kg/s.

How Much Air Must Be Pushed Downward at 60