4 thick books
1 piece of cardboard
Put the books in two piles about 15 cm apart.
Lay the piece of the cardboard on the books.
Put paper clips on the cardboard. Count them. The "bridge" starts to sag. Finally the bridge collapses.
Now make another bridge, but bend the piece of cardboard into an arch between the books.
Put paper clips and rubbers until it collapses.
This bridge is stronger than the first one.
The first bridge collapses before because it is flat and it has to take all the weight.
In the second bridge the weight goes to the sides and it is shared by the books, so the card can support more weight.
WHAT DO YOU THINK ABOUT IT? WRITE YOUR COMMENTS.