The tail rotor counters torque based on which physical principle?

• A. Bernoulli's Principle
• B. Newton's Third Law
• C. Conservation of Energy
• D. Ohm's Law

Answer: (B)

The main concept is action-reaction: the engine turning the main rotor applies a torque to the helicopter, and there’s an opposite torque on the fuselage. The tail rotor provides a counter torque by producing thrust that acts on the tail, creating an opposing moment on the helicopter structure. This balancing of torques keeps the aircraft from spinning uncontrollably and lets the pilot control yaw with pedals.

Bernoulli’s principle involves pressure differences and lift, not torque balance. Conservation of energy is about energy accounting, not the directional reaction forces between rotating parts. Ohm’s law is about electrical circuits. So the correct principle is Newton’s Third Law: every action has an equal and opposite reaction, which is exactly what the tail rotor uses to counter the main rotor’s torque.