The paper did not get stronger. So why can it hold the coins now?
Eve can say this.
The paper did not get stronger. So why can it hold the coins now? Fold it. Stack coins. Then try two mugs and a scrap of paper.
Words Eve says
The paper did not get stronger. So why can it hold the coins now? Fold it. Stack coins. Then try two mugs and a scrap of paper.
Two mugs, a sheet, some coins
Paper, mugs, coins. Keep stacks modest so nothing slides off a table.
Set two mugs a hand-span apart. Lay a flat sheet of paper across. Stack coins in the middle. Count how many before it drops.
Now accordion-fold a same-size sheet and try again.
Same paper. One change.
What else in the room is strong because of its shape, not its stuff?
Look closer
Notice
A flat sheet sags in the middle. That is the easy way for it to bend.
A fold stands up in the direction that used to be easy.
The paper is the same. The path of the load is not.
What do you think will happen?
Same strip of paper. Flat, or folded like a fan. Which holds more coins before it sags?
Change the shape of the span.
Keep looking
What must be true?
A load tries to bend the span in the easiest direction.
Folds make the paper thick in that direction, so the easy bend is no longer easy.
The material did not change. The geometry did. That is structure.
Shape is a kind of strength.
Engineers talk about how a beam carries a load, how the force travels to the supports without crumpling the middle. A folded sheet is a tiny beam. I-beams in buildings do a grown-up version of the same trick: put material where the bend would happen, and leave it out where it would not help. You can feel this with paper and coins. You do not need the vocabulary to see it.
A flat sheet of paper between two books collapses. Fold the same paper, and it can hold a load. The paper did not get stronger. A load tries to bend the span in the easiest direction. Folds make that easy bend no longer easy. Shape is a kind of strength. Try it with a book and a scrap of paper.
Words Eve says
A flat sheet of paper between two books collapses. Fold the same paper, and it can hold a load. The paper did not get stronger. A load tries to bend the span in the easiest direction. Folds make that easy bend no longer easy. Shape is a kind of strength. Try it with a book and a scrap of paper.
Beams, long before textbooks
People folded, corrugated, and vaulted long before anyone wrote “second moment of area.”
A reed boat, a corrugated roof, an egg: shapes that refuse the easy bend.
The paper bridge is the small version you can finish before supper.
- Exploratorium: Science Snacks · Hands-on structure activities with ordinary materials.
- National Academies: Teaching about structure · How load, shape, and material share the work in real structures.