Yet the proof is simple, and you can "experiment" when sitting on the lavatory, if the equipment is to hand.
If there is awall-mounted loo-roll, and the end is hanging down, blow between the paper and the wall, parallel with the wall.
You are adding air and might expect the paper to move away from the wall. It doesn't; it moves towards the wall as the faster air stream lowers the air pressure on on side of the paper and the air pressure in the room acting on the other side of the paper pushes the paper towards the wall.
Flight training should be undertaken in the lavatory!
Last edited by John R81; 21st May 2012 at 12:32.