If a hot air balloon is being carried by a continuous wind current in a particular direction, in which direction will the flags on its basket wave?
The balloon will asymptotically approach the wind velocity. As it gets close, the force due to drag will decrease because the apparent wind will be small. To the extent it matches the wind velocity, flags will hang straight down. To the extent it is (barely) below wind velocity, the flags will point (just a little) in the direction of the wind. If the wind slows down a bit, the flags will point backwards until the balloon slows down to the new velocity.