posted by Kyle .
During a rescue operation, a 5600-kg helicopter hovers above a fixed point. The helicopter blades send air downward with a speed of 69 m/s. What mass of air must pass through the blades every second to produce enough thrust for the helicopter to hover?
College Physics -
Strictly speaking, you also need to know the vertical velocity component of the air entering the blades from above. It is not zero.
They probably want you to use
Weight = V * dm/dt,
and solve for dm/dt, the air mass flow through the blades, but this is a flawed problem.
I do not endorse their answer