Final answer:
Helicopter blades rely on Newton's third law to counteract the rotational torque exerted on the helicopter body by the spinning blades, necessitating a tail rotor to stabilize the helicopter. Bernoulli's principle also plays a role in generating lift by creating a pressure difference across the rotor blades. Option A is the correct answer.
Step-by-step explanation:
Helicopter rotor blades function correctly due to several physical principles, but among the provided options, Newton's laws of motion, especially Newton's third law, is crucial for understanding the operation of helicopter blades, specifically regarding the rotation of the helicopter body and the necessity for a tail rotor. Newton's third law states that for every action, there is an equal and opposite reaction. Thus, when the main rotor blades spin, they exert a force on the air to generate lift. According to Newton's third law, the air pushes back with an equal and opposite force. This causes a reactive torque that would cause the helicopter body to rotate in the opposite direction of the blades if not counteracted by the tail rotor.
Moreover, Bernoulli's principle is also significant in explaining how rotor blades generate lift. The design of helicopter rotor blades is such that they create a pressure difference above and below the blades analogous to wings on an airplane, thus creating lift via increased air pressure underneath and decreased air pressure above the blade, utilizing Bernoulli's principle for lift generation.
If a helicopter has two sets of lifting blades rotating in opposite directions, it counteracts the reactive torque without the need for a tail rotor. This design applies Newton's third law effectively, as the opposite rotations cancel out the torques they generate on the body, stabilizing the helicopter's rotation without additional mechanisms.