n Transparent cup
n Index card
n Step 1: Fill the transparent cup with water.
n Step 2: Place the index card over the mouth of the transparent cup.
n Step 3: Hold the index card in place, slowly turn the transparent cup upside down, and then remove your hand from the index card. What happens?
The index card stays in place due to air pressure pushing up against the index card. The pressure pushing up is more than the weight of the water pushing down from the inside of the transparent cup therefore the index card stays in place.