Question

Problem 20

Answer 1

Given information

Consider a helicopter, it has one rotor or propeller.

 

Step-by-step explanation

Step 1.

The rotor of a helicopter has a specific angular velocity. To change this velocity an external torque must be applied on it.

The torque must be exerted by the helicopter.

According to Newton's third law of motion, every action has an equal and opposite reaction.

So, when the helicopter exerts a torque on the rotor it will also exerts the same torque on the helicopter in opposite direction. 

Therefore, when the speed of the rotor changes the helicopter also spin in a direction that is opposite to the direction of rotor's velocity.