Helicopters have a small propeller on their tail to keep them from rotating in the opposite direction of their main lifting blades. Explain in terms of Newton’s third law why the helicopter body rotates in the opposite direction to the blades.
According to Newton's third law, every action has an equal and opposite response.
When the propeller of a helicopter begins to spin, the helicopter's body follows the law and attempts to spin in the opposite direction.
The push or pull on a mass item that causes it to alter velocity is called force (to accelerate).
The main rotors, also known as main rotating blades, are horizontal propellers that raise the entire system. Torque is the force that causes it to rotate. It emanates from the helicopter's engine.
When the blades rotate in one direction, a reaction torque is created that opposes the blades' rotation. If the force rotates the rotor blades clockwise, the engine should experience an equal and opposite counterclockwise force.
As a result, the helicopter's body will also revolve counterclockwise. Finally, the body of the helicopter tries to spin. Newton's third law explains this quite well.
When the helicopter is on the ground, friction (another force) prevents it from rotating; but, once in the air, there is no opposing force, and the body spins in the opposite direction as the rotor blades.
Consider the Earth-Moon system. Construct a problem in which you calculate the total angular momentum of the system including the spins of the Earth and the Moon on their axes and the orbital angular momentum of the Earth-Moon system in its nearly monthly rotation. Calculate what happens to the Moon’s orbital radius if the Earth’s rotation decreases due to tidal drag. Among the things to be considered are the amount by which the Earth’s rotation slows and the fact that the Moon will continue to have one side always facing the Earth.
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