Question

Why there are two propellers in a helicopter ?

• A. Due to conservation of linear momentum, the helicopter itself would have turned in the opposite direction, if it had only one propeller
• B. Due to conservation of angular momentum, the helicopter itself would have turned in the opposite direction, if it had only one propeller
• C. The helicopter can't rise up with one
• D. The helicopter would not gain speed with one

Answer 1

Answer: (B)

If there would be only one propeller, the helicopter start rotating in the direction opposite to the movement of the propeller. The two propeller rotate in the opposite direction as to cancel the torque produced by one propeller