During a rescue operation, a 5300kg helicopter hovers at a fixed height. The rotor blades send air downward at a speed of 62m/s. What mass of air must pass through the blades every second to produce enough thrust to hold the helicopter in place?

Question

anonymous · Answer

|dw:1320718007338:dw|

Sistem: Helicopter(mass: 5300 Kg)
Surroundings(Earth, Air)
Initial State: vi=62 m/s
Final State:  

FBD:
|dw:1320718388947:dw|

F = mass * acerelation 

Fgrav = mHelicopter * g     
Fgrav = (5300 Kg)(-9.8 m/s^2)
Fgrav = -51.94 m/s^2

Fblades(helicopter) = mAir * aAir
Fblases/vAir = mAir

Fgrav = Fblades(helicopter) Proportial (ie: equilibrium. hovering)

mAir = 51,94 m/s^2 / 62 m/s = 873.74 Kg/s^2

Therefore 873.74 Kg of air pass through the blades every second for the helicopter to remain in the air (hovering).

anonymous · Answer

I made drawings and the FBD but OpenStudy lag so much that didnt let me post it, so I had to refresh and copy the whole solution again... Still it works.