Compression and Tension
Compression and tension is how parts of a structure get pushed together or pulled apart when it holds a load.
When you stack heavy cans on a shelf, the shelf bends slightly in the middle. The top surface gets squeezed together — that is compression. The bottom surface gets stretched apart — that is tension. The shelf holds the load by balancing both forces at once.
Explaining compression and tension by grade level
Stand on an eggshell arch. The top gets squeezed. The bottom gets stretched. That squeeze is compression. That stretch is tension. Strong shapes like arches spread the push and pull so they do not break.
Projects that explore compression and tension
When you stack books on egg domes, the curved shape pushes force out and down. That spreading push is what squeezes the shell — putting it in compression. No single spot bears too much force because the dome distributes the load across its whole surface.
Bending plywood strips into arches that all stand 100 mm tall but span different widths reveals how geometry controls where a structure gets pushed together or pulled apart under load. As the span increases, the arches fail under less weight — wider diameters without added height shift more of the load into pulling forces the plywood cannot resist.
As force travels along an arch's curve, it splits into two parts. Compression squeezes the material along the surface, while tension pulls at the base where the arch meets its supports. A 650 mm strip creates the strongest arch because its height balances these two forces so neither overwhelms the plywood.