(a) Why do most small helicopters have a rotor on their tail (Fig. Q9.17)? (b) Many larg...

(a) Why do most small helicopters have a rotor on their tail (Fig. Q9.17)? (b) Many large helicopters have two large rotors. Why do these helicopters not need a tail rotor? Do you think the two large propellers rotate in the same direction? Explain.