A nice simple puzzle.Have a look at this for a question I found at Tempus Fugit.
If an airplane is on a large conveyor belt and is trying to take off by exerting the thrust needed to move it forward at 100 knots, and the conveyor belt starts moving backwards at 100 knots, will the plane be able to take off, or will it just sit stationary relative to the ground, with the backwards speed of the conveyor belt counteracting the forward thrust of the plane?
It looks and sounds simple but there are some major discussions going on about it. Read the full story and some of the comments. Don't subscribe because I got 30+ EMails from it in a couple of days all arguing the same thing from one or the other viewpoint. It will fly or it won't fly.