Is that sheet of newspaper
really that heavy?
All
you need to convince your child that air pressure isn't imaginary is a
ruler (wooden), a countertop/tabletop, and a newspaper.
1.
Place the ruler on the countertop with about 3-4 inches jutting out.
Give a quick tap on the part of the ruler jutting out (i.e., not over
the counter). Of course, the ruler should fall/fly out.
2. Next
place a sheet of newspaper over the ruler on the counter. Try
to
find as big a newspaper sheet as you can find. For example,
the
middle two sheets that are attached should work well. Flatten out the newspaper as much as you can with
your hand.
3. As you did in Step 1, strike the ruler again. Hit it
as hard as you can. Don't press the ruler down, but rather give it a
sharp hit. The newspaper will hold the ruler down, even if you strike hard at the ruler.
Explanation:
It is the air pressure. Well,
actually, that's part of the answer. When you give the ruler a quick
tap, the
other side (under the newspaper) will try to come up. This will create
a pocket with very low pressure. This low pressure on one side and the
normal air pressure on top is what keeps the newspaper down.
If
you push the ruler down, some air will sneak in under the newspaper and
without significant difference in pressure on the two sides, the
newspaper will not keep the ruler down. That is why you need to hit the
ruler quickly.
Try to hit the ruler hard. You can easily break the ruler (see picture).
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