Folded Bridges: Accordion and Box

Fold the paper into an accordion pattern (also called a fan fold): fold one way, flip, fold the other way, flip, and repeat until the whole paper is folded into ridges.

Place this accordion bridge across the gap and start adding coins. How many can it hold?

Usually the accordion fold holds 10-20 coins or more! That is way more than the flat paper. Why? The folds create ridges that resist bending. Each fold acts like a tiny wall that pushes against the weight.

The corrugated shape spreads the force across the whole bridge instead of concentrating it in one saggy spot. Cardboard boxes use this same principle: corrugated cardboard has wavy folds inside that make it strong!