Making Maths: Test the Strength of a Triangle

Stage: 2 Challenge Level:

Have you noticed how many triangles are found in manmade structures? There is a good reason for that. Even when weak or flexible materials are used to build triangles they are still pretty strong. This is because triangles are rigid shapes. 'Test a Triangle' and see how rigid it is.

You will need:

Drinking straws
String

What to do:

Tie a knot at one end of a piece of string and thread the other end through a straw.
Tie a large knot in the string where it comes out of the straw.
Thread the string through a second straw and tie another large knot in it where it comes out of the straw.
Thread the string through a third straw and tie the string to the first knot.
This will form a triangle. Cut off the extra string.

Try to bend your triangle.

Does it bend out of shape easily?

Use additional straws and string to make squares and other shapes.

Experiment to see which shapes are the most rigid, that is to say will bend the least under pressure.

Which shapes do you recommend to use for structures like buildings and bridges?

This activity features in our December 2008 Advent Calendar .