Triangles in Construction

A popular activity in nurseries is building structures. Many interesting questions can arise when children experiment with building specifically, why are triangles stronger than squares?

If we apply force to a square, it can become a rhombus via a change in angles. Children can experiment with cardboard boxes to see this change, which is shown in the image below.

Unlike squares, triangles have angles that are determined by the relative lengths of the sides. This means if we wanted to change the angles between the sides of the triangle, we would also have to change the length of the sides. If the material of the triangle is not elastic, the only way the lengths of the sides of the triangle would change would be by the material deforming. Of course, both the square and the triangle will eventually deform under enough force, depending on the strength of the materials used.

It might be interesting for the children to conduct some experiments to see how much weight a cardboard box can hold and how this increases by adding a diagonal beam splitting the square profile into two triangles. In the images below, we can see that the box with the beam can hold both the pen and the marker lid, whereas the box without the beam is about to collapse when only supporting the marker lid. This is because the beam splits the square into two triangular segments, which are harder to deform.

A fun activity for children might be to recognise how triangles are used throughout familiar architecture. Many bridges use triangles in their construction. The Tyne Bridge in Newcastle, shown below, has many triangles in its arch.