A driver is taking a truck full of birds over a bridge but the truck and cargo weigh too much. If he can get all of the birds to fly at the same time, can he bring the total weight down?
The first new player to comment on the website with the correct answer wins a free drink at their next iQ Trivia show.
It depends to an almost trivial extent on whether the birds are in a cage that allows air in from outside. If there is no air exchange the inside air will get pushed down by their wings and exert a downward force on the bottom of the container equal to the weight of the birds. If some air can escape, a very small amount of the downward thrust will go outside the truck.
He would probably do better by stripping off some clothes and going back for them later!
Yes if it is a sealed system, that force has got to go somewhere. No way around it.