Triangles have many practical uses in the real world. They often exist in corrugated forms, where there are series of triangles right next to each other supporting an object. An example of this is in cardboard, which is a type of reinforced paper. What makes corrugated cardboard so strong is a layer of paper triangles sandwiched between the two layers of flat paper. Since triangles do not bend easily, two layers of paper with the paper triangles between them are stronger than the two layers of paper would be without the triangles.
The diagram on the right is of a piece of cardboard. When a force presses down on the cardboard, the surface experiences a compressive force (e.g. a force that bends or folds the paper at the point of stress) and also a tensile force (e.g. a force that stretches paper at the bottom in order to let the upper surface of the cardboard bend). The paper does not bend easily however, because the numerous triangles spread the force out among several points, rather than concentrating the force on one spot.
Using Cardboard at Home:
Try making a Super Strong Sled using corrugated cardboard! NOTE: you will need the help of a grownup for this activity!