Briefing
What's inside an empty cup? What's weighing down on the grass in an open field? What's strong enough to hold up a truck or knock down a tree? The answer to all of these is air! Think the air's just a whole lot of nothing? Try this Fab Lab and see for yourself!
Activity
What You'll Need:
Paper towels
A clear plastic cup
A watertight container deep enough to contain the entire cup
A few sheets of newspaper
A ruler, yardstick, or wooden stick at least 12 inches long
Part One: Dunk!
1. Fill the container about halfway with water.
2. Crumple up a paper towel and stick it in the bottom of the cup. Pack it in tight, so it doesn't fall out easily.
3. What do you think will happen to the paper towel if you put the cup in the water upside down? Write down your answer before you move on.
4. Turn the cup upside down and slowly sink it into the water. Keep going until the entire cup is underwater.
5. Slowly bring the cup back out of the water.
6. When the cup is completely out of the water, flip it back over and take out the paper towel.
7. Write down your observations. Is the paper towel wet or dry? Why do you think that is?
Part Two: Flip!
1. Place the ruler or wooden stick on a table. About half of the stick should hang over the edge of the table, like a diving board.
2. Tap the end of the stick that's hanging over the edge of the table very gently. Then tap it with a little more force. Keep doing this until the stick flips off the table.
3. Try this a couple of times. See if you can feel exactly how much force it takes to make the stick flip over.
4. When you're ready, put the stick back on the table again. This time, lay a piece of newspaper flat over the part of the stick that's on the table. (Half of it should still stick out.) The newspaper should be perfectly flat, with no air under it.
5. What do you think will happen when you hit the stick now? Write down your prediction.
6. Tap the stick with the same amount of force as before. What happened? Tap it harder if you need to. See how hard you have to hit it to make it flip over.
7. Crumple up the newspaper into a ball. Put it back on top of the stick and hit it again. What happened this time?
Debriefing
What kept your paper towel from getting all wet? The answer is air! When you sunk the cup into the water, there was air trapped between the water and the paper towel. The air takes up space, so the water couldn't go all the way into the cup and get the paper towel wet.
How about the stick? You guessed it -- air again! When the stick was under the flat newspaper, it was pinned down by all the air weighing down on the surface of the paper. In fact, the air can put thousands of pounds of pressure on just a normal-sized piece of paper.
If you've got your Case Journal, go ahead and answer the questions in it now!