Heavy Paper-Exploring the Power of Air

How Does It Work

The results of the activity demonstrate that the newspaper is difficult to lift when it’s spread out over a large area. What force other than gravity is exerted on the newspaper that could account for this? The answer is as simple as the air we breathe. It’s the pressure of the air weighing down on the newspaper that prevents the paper from rising and holds the stick in place under it.

It might be useful to picture a giant column of air weighing down on the newspaper. This column of air is about 250 miles (402 km) high and at sea level, it presses down with a force of 14.7 pounds per square inch (76 cmHg). In other words, each square inch (or square centimeter) of the newspaper has 14.7 pounds (6.7 kg) sitting on it.

Take It Further

You can do this activity as a very interesting demonstration for a group. Besides, a little humor helps the audience and it always makes science more fun… if that’s even possible.

1. Place the stick on the table as before. Ask your spectators, “What will happen if I hit the end of the stick hanging over the edge of the table?” Make sure everyone is out of the way and smack the stick. Of course, the stick goes flying end over end as predicted.
2. Return the stick to the table again. “Let’s use a piece of newspaper to help hold the stick in place.” Show a single sheet of newspaper and fold it in half 3 or 4 times. Center the folded newspaper over the half of the stick on the table. Make sure it’s safe to do so and then hit the end of the stick. Once again, the stick goes flying and the paper flies off, too.
3. Finally, show your spectators a new, unfolded sheet of newspaper (or use two if you like) and use it to cover the half of the stick on the table, centered as before. Line it up with the table edge as before, too. “What will happen this time when I hit the stick?” You might anticipate answers like, “The newspaper will go flying” or “The sheet of newspaper will tear apart.” Smooth the newspaper and strike the stick as you did earlier. To everyone’s amazement, the stick either (1) breaks or, (2) lifts sharply off the table but flattens back immediately. Remind the audience that the weight of flat newspaper is exactly the same as the folded newspaper, yet the unfolded newspaper stayed in place and held down the stick. Take a bow and do the math for the skeptics!

A look at the numbers

If you know the area of the newspaper page, you can calculate the total pressure pushing on it. Say that the opened newspaper page measures 30″ x 23″ (76 x 58 cm). That area is 690 in² (4408 cm²). If each in² (2.5cm²) has a force of 14.7 pounds (6.7 kg) pushing on it, then 10,143 pounds (52, 454 cmHg) are holding it down! It’s no wonder the newspaper stayed in place when you hit the stick. Smoothing the newspaper prior to striking is an important step. You need to make certain there is no air trapped under the newspaper. It allows the paper to lift more when you strike the stick.