Where’s the pressure difference in this trick?
At the opening of the glass. The water inside the glass weighs a pound at best, and, depending on the size of the opening of the glass, the air pressure is exerting 15-30 pounds upward on the bottom of the card. Guess who wins? Tip, when you get good at this experiment, try doing it over a friend’s head!
Materials: a glass, and an index card large enough to completely cover the mouth of the glass.
Please login or register to read the rest of this content.