Can paper hold up 20 coins?

You will fold a paper bridge and test how many coins it carries. A flat sheet bends easily, so the challenge is to change its shape without adding support.

Build
Explorer
About 10 minutes

Help needed: yes for setup, nearby supervision and clearing spills or loose pieces

What you need

One sheet of paper
Two similar books
Coins selected by someone

The rule

No tape. No glue. Folds only.

How to do it

Set two books a small hand-width apart on a level table.
Fold the sheet backwards and forwards into equal zigzags.
Lay the folded sheet across the gap with both ends resting on books.
Ask someone to place one coin at the centre.
Count each extra coin until the bridge first sags or slips.
Record the count before rebuilding with a different fold depth.

Why it works

A fold moves some paper away from the middle of the bridge’s thickness. That changed shape makes bending harder, even though you have not added more paper. The books support the ends while the coins push down between them. Deep folds can resist bending better than shallow ones, but the bridge can still twist, slip or flatten. Your coin count is a test of this bridge and this gap, rather than a promise about every sheet.

Make it harder

Widen the gap slightly.
Try shallower folds with the same gap.
Design a shape that holds the same load with fewer folds.

Ask Taz

Why does folded paper bend less easily?
Why does a wider gap make the bridge harder to support?
Why can the bridge twist before it breaks?

Ask Taz

Before you start

Watch whether the learner changes the fold depth or the gap, and help them keep the other choice steady. The activity connects shape with strength and introduces a fair comparison. Ask at dinner: “Which change made the biggest difference to your bridge, and what evidence made you think so?”

Taz is an AI and can be wrong, so check what matters. Read how safety works on Taz.

Show us yours

Film your hands and what you made, not your face or name. If you are under 18, ask a parent or guardian before posting anywhere else.

Common questions

Do we need special equipment?

Use the household items listed above. Begin with a small attempt on a clear surface before trying any harder version. The listed time is an estimate, so leave room to rebuild or repeat without rushing.

What if the first attempt does not work?

Notice where the result first changed. Alter one feature, keep the rest similar and try again. An unsuccessful attempt can still give you a useful question.

Do we have to post the result?

No. You can show it to someone at home. Online sharing is optional and needs the permissions in the privacy line above.

More to try

See all Taz Challenges, or look through the science labs. One place for every why. Start exploring at aitaz.com

Try it in 3D: Bridge design.