This week we will investigate the
world of engineering. Instead of
building a skyscraper, we will are going to build a bridge. Often,
bridges can cost millions of dollars, but this one will only require a
single dollar bill for its construction.
You will need:
2
drinking glasses a
dollar bill 8
quarters or other coins
Place the two glasses on a flat
surface, upside down. Place them far
enough apart so that a dollar bill will reach from the center of one
glass to the center of the other. Your task is to use the dollar bill
to make a bridge from one glass to the other. Your bridge must be
strong enough to support the weight of 8 quarters in its center. Take a
moment and try it.
By placing the dollar flat on the
glasses, it will not even support one
quarter, much less all eight. How can we strengthen the dollar? There
are a lot of people in the government that would like to know that.
To add strength to the paper, we
will fold it. Start at the top of the
bill and fold 1/4 of an inch of the paper towards the front of the bill
and crease it. Then fold the next 1/4 of an inch towards the back of
the bill. Keep making a fold each 1/4 inch, alternating between folding
towards the front and back, until you reach the bottom. When you
finish, the folds in the bill should look something like this: VVVVVVV
Once you have all the folds,
place the bill across the two glasses and
gently place a quarter in the center. Your "bridge" holds it up. Add
another quarter and another. You should be able to easily get the
dollar bill to support all 8 quarters.
Folding the bill changes the
lines of force in the paper. This folding
is called corrugation and it is very useful for making things stronger.
If you cut through a cardboard box, you will see the same shape. It is
made up of a corrugated piece of paper, glued in between two flat
pieces. Again the folding makes the paper stronger, forming a very
strong box made of thin, light paper. Look around and see if you can
find other things that use the same idea. Be sure to notice the metal
siding on buildings, the construction of bridges and other structures
that need to be very strong.
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these
experiments on my web site.
