Heavy Newspaper – SICK Science
A few pages of newspaper and a yard or meter stick reveal atmospheric pressure in a surprising way.
Everyday you feel it but you don’t even know it’s pressing on you. You walk with it, you run with it, you sleep under it, and you keep ignoring it. Even as you read this, it’s pressing relentlessly down on you. The air in the atmosphere brings weight to bear on you every second but you’re used to it and don’t realize you’re dealing with it.
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- Yard or meter sticks (furring strips work)
- Full newspaper pages (butcher paper works)
- Work gloves
- Table with a straight edge
- Safety glasses
- Adult supervision
Place a yard or meter stick on a table so that half of it hangs over the edge.
Lay a page or two of the newspaper over the stick on the table like a blanket. The center fold of the paper should be on top of the stick and a long side of the paper should be flush with the edge of the table. Smooth the newspaper so there are no pockets of air under the paper.
Put on your glove to protect your hand and wear the safety glasses to protect your eyes. Use your hand to strike the protruding end of the stick with a sudden, sharp hit.
The flattened newspaper pretty much stays in place and holds the stick in place, too. You don’t have to break the stick to prove to yourself that there’s something besides gravity holding the paper on the table.
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.
- 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.
- 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.
- 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.