dishpan or something to catch water in
Do not use a paper or foam cup. It will dent in when you hold it and break the seal with the cardboard and allow the water to pour out.
Cut a square of cardboard a little larger than the top of the cup. Make siure the cardboard is smooth. Fill the cup 1/4 to 1/2 full with water. Place the cardboard over the top of the cup and turn it upside down. carefully remove your hand holding the cardboard in place. do this over a container to catch the water (in case you mess up) the cardboard will stay in place.
The pressure of the atmosphere will push up on the cardboard and hold it in place. At one atmosphere the pressure of the air is 14.7 lbs/in squared
The Daily News
Yard stick - thin wood - can be found at most hardware stores for about 50 cents
Place the newspaper on the table. The paper should have two full pages open. Measure the lenght and width of the paper in inches and record it.
Place the yard sick on the table. About 12 to 14 inches of it shold be over the end. Lay the paper over the ruler and smooth it down. The paper must be flat on the table. It cannot have areas up to allow air to get under it.
Flex your muscles, and give it a karate chop near the table and the paler will hold it down. If you chop it to far away from the table, the ruler will act like a lever and lift the paper up.
How does this work?
Air at one atmosphere of pressure exerts a pressure of 14.7 lbs/in squared.
Have the sutdents multiply the length x width of the newspaper to find the area of it. Then multiply the area by 14.7 lbs/in squared and this will give you the force that the air is pushing down on the newspaper. this is a large force and is much greater than the force you apply with the ruler lifting up the newspaper. It holds the ruler down and it breaks.
Feeling Air Pressure
large garbage bag - larger than 30 gallons if you can find them for a high school student