Quote:
Originally posted by ryph
yes, actually
think of it when a helicopter takes off, the propeler exerts a force greater than its weight onto the ground to lift off. and in order to stay flying, must exert the same amount of force as its own weight. otherwise it will drop.
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You're sort of right but you're entirely wrong. To fly, a bird or helicopter does have to exert force but that force doesn't necessarily make it to the ground, at least not all in one place. The force is distributed and diminished over area, some of it surely laterally. If your theory was true, anyone ever rescued by helicopter would have been crushed to death by the downforce of the machine over them. Every movie that ever showed a helicopter pass over a car would have resulted in a smashed car. Just think of what would happen to spectators at air shows.
There is no way that 200 kilograms of bird in flight transfer their full 200kgs to the ground beneath them. Has a bird ever flown directly over you? Probably. Did you notice extra weight? Probably not. Would you have noticed extra weight if the bird sat on your head? Probably.
SpaceAce