Most helicopters have a tail boom and tail rotor. This tail rotor is present to counteract the torque produced by a helicopters main rotor. If there was no tail rotor, the helicopter would tend to rotate in a direction opposite to that which the main rotor blade spins which would make flying difficult or even impossible.
The Chinook doesn't have a tail rotor, instead it has twin main rotors. If they both span in the same direction then this would act to cause the helicopter to twist. However as they rotate in opposite directions the two twisting forces cancel each other out. This has other advantages as it means that the full power of the engines goes towards generating lift and thrust as opposed to driving the vertical stabilising rotor on other helicopters.
Helicopters don't just have 3 blades. It depends on the size and weightlifting capability. Small helicopters such as a Robinson R22 have only 2 blades, the military Merlin has 5 and the Chinook has two rotors with usually 3 blades each.
Helicopters do not defy gravity. They generate lift through their rotating blades, which pushes against the force of gravity to keep them airborne. Without this lift, helicopters would fall to the ground like any other object under the influence of gravity.
The rotor blades lift helicopters
The rotor hub holds blades on
Helicopters have 2 sets of blades to keep the helicopter balanced. This is due to the unique shape of the helicopter.
Rotor blades
Chinook can hold about 19,500 lbs,otherwise the hooks could cut off by the rot er blades.
the helicopters are bigger so there needs to be a greater weight distribution
Older helicopters had noisy rotor blades, modern ones are very quiet.
No!
Yes, many small helicopters have 3 blades
In helicopter terms, the Rotor is actually the set of blades as a whole, individual blades are termed to be the rotor blades. So if you negate the Chinook, and a few other unusual types of helicopter, all helicopters utilise a single rotor. If you mean a single rotor blade, well again a single rotor blade design has been used on a helicopter.... An example of this was the Hiller HJ-1 Hornet, also the Boelkow 101/103 are good examples of this design.