Final answer:
Helicopters have a horizontal stabilizer and a tail rotor at the tail end to maintain stability and counteract the torque caused by the rotation of the main lifting blades. Rotational kinetic energy is crucial for helicopter flight, and dual-rotor designs rotating in opposite directions enhance stability and efficiency.
Step-by-step explanation:
Many helicopters have a horizontal stabilizer located at the tail end of the aircraft. This stabilizer plays a crucial role in ensuring the helicopter maintains a stable flight attitude and aids in pitch control during forward flight. Helicopters are equipped with a small propeller on their tail, known as the tail rotor, which counteracts the torque effect created by the main rotating blades. According to Newton's third law of motion, for every action, there is an equal and opposite reaction; thus, as the main rotor spins in one direction, the helicopter body wants to spin in the opposite direction. The tail rotor provides the necessary thrust to counteract this rotational force.
Additionally, helicopters store a significant amount of rotational kinetic energy in their main blades. This energy must be imparted before takeoff and maintained until the helicopter lands, as the engines alone do not have sufficient power to both lift the helicopter and impart substantial rotational energy to the blades simultaneously.
In helicopters with two sets of lifting blades that rotate in opposite directions, this counteracts the torque effect, eliminating the need for a tail rotor. This design is beneficial because it provides greater stability and control and maximizes the efficiency of the helicopter's lift-generating capabilities.