## How strong is paper? Let’s find out with two simple science experiments!

Testing material strength is such a fun engineering activity for kids. We’ve tested to see how strong spaghetti is. And now we’re going to test the strength of a sheet of paper.

You can use materials from around your house or classroom to conducts these experiments.

Supplies Needed:

• Copy paper – we used colored paper, but plain white works just as well
• Tape
• Books
• Other weights such as cans

## Experiment #1: How Strong is Corrugated Paper?

If you put folds in a sheet of paper, what effect will that have on its strength?

Step 1: Create a bridge. We used cans as the supports for our bridge. Lay a sheet of paper across the cans. Will this sheet of paper hold up the can? We used a small can, but everyone knew it would not hold up the can!

As predicted, the piece of paper did not hold up the can even for a moment!

Step 2: Create a corrugated sheet of paper by making small folds in the paper.

Try to fold the paper as evenly as possible but it doesn’t have to be perfect.

Try your bridge again. Now the paper will EASILY hold a small can!

In fact, our corrugated paper bridge was able to hold a larger 16 oz can!

Step 3: Compare lots of folds with a few folds.

The pieces of paper in the photo below are the same size. But the green paper on the right was folded more times.

Which is stronger, corrugated paper with more folds? Or less folds?

We guessed that more folds would increase the strength.

And it did! We were able to balance both cans on top of our tightly folded paper. In addition, the paper just FELT stronger when I was placing the cans on it.

### Why is corrugated paper stronger than regular paper?

Adding folds to the paper compresses the paper (along the folds) and makes it more rigid and much more resistant to bending. The paper now has stiff struts that give it strength.

With folds running lengthwise, you are now unable to bend the paper widthwise without creasing it.

## Experiment #2: Which Shape is the Strongest?

In this experiment, we’re going to test paper columns in two different shapes to see which shape is the strongest.

We chose to compare circles and triangles. If you have the time, it’s fun to also compare squares.

Roll two pieces of paper into circular columns and tape them. Then fold two pieces of paper into triangles and tape them.

It doesn’t seem like pieces of paper will be able to hold up any weight at all, but both shapes are surprisingly strong.

We balanced a few books on top of our circular columns and could tell that we were going to be able to add a LOT more weight.

Look how many books the circular columns supported!!! WOW.

The columns crumpled shortly after this photo. But they sure held a LOT of weight!

Keep in mind that you are looking for the paper to buckle, not for the stack to tip over. If the books tip, then they aren’t balanced correctly. You want to see how much weight the columns can handle before the paper starts to give way.

## How do paper columns hold up this much weight? And which shape is the strongest?

Both the triangle and the circle shaped columns are distributing the weight of the books around the perimeter of the shape.

We found that our circular columns could hold more weight than the triangles.

The circular columns are the strongest because without corners, they balance the weight evenly around the whole circle. This may come as a surprise if you know that triangles are the strongest shape! Triangles ARE the strongest shape when it comes to building supports in bridges, etc. But in this application, the circle has the advantage.

One thing that is a little tricky about this experiment is that it’s hard to add weight in even amounts. Our books did not all have the same mass. If you want to make this experiment more precise, try using identical wooden building blocks for your tests. If you’re in a classroom, you may have a class set of books that are all the same. For example, 25 copies of the same title or something like that.

## Need more engineering activities for kids?

Build some Marble Trampolines with a cup and a balloon! These are super fun and a great addition to any marble run. This activity really gets kids thinking, and you probably have the supplies on hand.

I HIGHLY recommend this Laser Puzzle Box Activity. You’ll need some laser pointers, but kids will love this. Challenge them to use mirrors to get the laser to enter one hole in the box and leave through a different hole!

Challenge kids to design and build a Straw Roller Coaster. You can use paper straws if you prefer avoiding plastic, but the cost will be much higher. Besides straws, you just need a glue gun and some cardboard for the base!