When viewed from above, suppose that a helicopter’s rotor spins clockwise. The helicopter engine must continually exert a torque on the rotor to keep it spinning against the drag that the air exerts on the rotor. Note that a helicopter is usually designed so its center of mass is directly under the rotor. In order for the helicopter to hover motionless in the air, a small rotor at the helicopter’s tail is necessary. As viewed by someone looking at the tail from the helicopter’s front, the small rotor must blow air
A. To the left.
B. To the right.
C. Vertically upward.
D. Vertically downward.
E. In some combination of these directions.
A. To the left.
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