A jar is filled to the top with water, and a piece of cardboard is slid over the opening so that there is only water in the . If the jar is now turned over, will the cardboard fall off? What will happen if there is any air in the jar?
If you do it carefully enough, a small amount of water will pour out of the glass — that's supposed to happen. But try not to let any air bubbles get into the glass. Finally, slowly remove the hand holding the cardboard in place.
