Question

Why does a Helicopter have at least two rotor blades . ? Anything related to rotational motion?

Answer 1

the tail propeller is for stabilization
it prevent the body from rotating with the main propeller

Answer 2

The existence of two rotor blades is to balance the centripetal force of the spinning mass.

Answer 3

It will be rather awkward to have only one rotor blade. Try to open the cap of a bottle by using only one finger. Its more difficult than to use two fingers, which rotate the cap in the same direction.
Thus, a rotor must be doing something similar. Two blades rotate in the same direction, creating the effect of a couple force. Thus, it creates the lift required to support its weight more successfully.

Answer 4

By two blades i mean :

Answer 5

Same thing, for stability.
Everything on a Helicopter is special crafted for stability. The double blades is for double the push on the ground to gain extra force of lift. Thats it nothing to it.

Answer 6

The more blades you have the more lift you can generate due to the increased surface area of the blades. Having more lift means you can carry heavier loads. More blades also reduces vibrations through the rotor hub.

Answer 7

Some helicopter only have one blade