Nick

I'd appreciate any answers to this logic conundrum. Thanks. Engineers are confronted with two apparently true but contradictory statements: a) To fly, lift must equal the weight of the airplane (Lift = Weight). b) Commercial airliners such as Boeing 747-400 and Airbus 320 have thrust-to-weight ratios of about 0.3. i.e. Thrust / Weight = 0.3 If the engine thrust (Thrust) is 3N, then the weight must be 10 N, and the Lift must be 10 N as well. But there is a significant problem: According to this logic, 10 N of Lift is 7 N greater than the 3 N of Thrust. This is impossible as 3 N of Thrust cannot produce the Lift of 10 N. Hence a paradox arises, as equations (a) and (b) appear true when stated individually. But combined they produce equation (c) ‘Thrust / Lift = 0.3’ that is false (i.e. impossible). Therefore, one of the equations (a) or (b) must also be false. But which one?