A stone arch without mortar

Nine wedge stones hold each other and a load on top. Remove the keystone and the arch collapses.

2D Age 9+15 min StabilityGravity

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Press “Run”. Bodies move by the laws of physics: gravity, friction, elasticity.

What the experiment shows

Each wedge leans on its neighbours. Weight pushes down, and the arch shape turns it into compression along the curve that flows to the supports.

How to run it

Press “Run”: a load drops onto the arch.
In the editor delete the top (key) stone and run again.
Remove the side supports — what happens?

Questions to discuss

Why do Roman bridges stand for 2000 years without cement?
Where do the stones press hardest?

The science

Stone is weak in bending but strong in compression. An arch steers the forces along its curve so the stones are only squeezed. Heavy abutments hold the outward thrust at the base.

Try it at home

Build an arch from foam pieces or sugar cubes over a cardboard form, then pull the form out.

What to change in the editor

Reduce the stones’ friction.
Make the load heavier.