‫And now let's look at how those forces in moments are created by those propellers.
‫Let's start from the top few of the drone.
‫We have four motors, motors, one and three rotate counter-clockwise and motors two and four rotate
‫clockwise.
‫Why is it necessary that two of them rotate in the opposite direction to the other two?
‫Well, let's think of a helicopter hovering in the air.
‫What will happen to it if you lose its tail?
‫Let's say that you shut it down.
‫Now you only have the big propeller working.
‫The Newton's third law says that if you push an object with a specific force, then that object pushes
‫you with a force that is equal in magnitude and opposite in direction.
‫A similar thing happens with rotations inside the helicopter.
‫You have some kind of engine that applies to work to the main rotor that makes it rotate.
‫And so the rotor applies to talk to the rest of the helicopter, which is equal in magnitude, but opposite
‫in direction.
‫In other words, as the main rotor rotates counterclockwise, the rest of the body will rotate clockwise
‫and vice versa.
‫Of course, the helicopter will rotate slower than the rotor.
‫However, that is due to the fact that the mass movement of inertia of the helicopter around the axis
‫of rotation is bigger than the one of the rudder.
‫Remember mass moment of inertia, resistance to rotation.
‫The bigger it is, the harder it is to rotate the object.
‫And so the objective of the tail in the helicopter is to create a counter torque that keeps the chopper
‫rotational at rest.