Here is a super-cool demonstration of something outrageous...
What you need. . .
• A newspaper
• A wooden ruler you wouldn't mind destroying, or a flat wooden stirring stick like the kind used to stir paint.
• A broom handle or a wooden dowel for whacking
(Click to enlarge image.) First, if you use a ruler, make sure to pull the metal pencil guide out of the grove in the side and throw the guide away.
(Click to enlarge.) Place your ruler so that its center is just over the edge of a table that has a hard and straight edge, as shown in the photo. Now, imagine you were to use a broom handle to give the overhanging edge a hard whack, as shown. What do you think would happen? Write your prediction down in your science journal and then, make sure everyone is well clear of the table and do the experiment!
(Click to enlarge.) Next, ball up a single sheet of newsprint and balance it on the ruler as shown. Now what do you think is going to happen to the ruler and to the paper ball when you strike the ruler hard with the broomstick? Write down your prediction in your note book, STAND BACK, and do the experiment!
(Click to enlarge.) Now, pick up a new sheet of newsprint. Only this time, lay it out flat over and the edge of the table as shown, and slip the ruler underneath it so that it is sticking out halfway as before. The sheet weighs the same amount whether it is balled up or flat, right? So the weight of the paper is the same in both trials. What do you think is going to happen this time? Write your prediction down and explain it in your science journal.
Go ahead and do the experiment. I'll wait. . .
Pretty cool, eh?
Here's a photograph of what happened when I did it. If you hit the end flat, your ruler should have broken. If you hit it at an angle, so the ruler tipped sideways a little, then it probably ripped a ruler-shaped slot out of the newspaper. The point is, something got broken!
(Click to enlarge.) When you laid the newspaper out flat something had to give.
Here's why… When laid flat, the newspaper acts a little like a diaphragm because it's hard for air to slip underneath it very quickly. Hitting the stick causes the other side to lift the paper quite rapidly, far faster in fact than the air can flow in to fill the gap. Essentially, the air above the paper can't get out of the way as fast as the stick wants to move it. As a result the atmosphere just sits there and clamps the sheet to the table.
That's why something has to give. Either the stick has to break or the paper has to tear because the atmosphere won't let the paper get out of the way fast enough. (Here's another test of this idea. Try pushing on the stick slowly. Does anything get torn or broken? Can you explain why or why not?)
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