# Corrugated Paper

Triangles are just plain and boring, right? Wrong! Use the mighty power of triangles to help your plasticine man survive the weight of a block of wood.

• Mathematics > Measurement and Geometry > Year 3 > ACMMG063
• Science > Physical Sciences > Year 4 > ACSSU076

## You'll need

• 2 x A4 sheets of paper
• 3 blocks of wood
• plasticine

## Try this

1. Make a house by using two blocks of wood for the walls and a sheet of paper for the roof.
2. Use plasticine to make a figure of a man that can fit inside the house.
3. Place the plasticine man in the house and test the strength of the roof by placing the third block of wood on the paper roof. The roof will cave in and the man will be squashed.
4. Re-shape the plasticine man.
5. The next step is similar to making a fan. Using the second sheet of paper, fold the shortest end over and make a straight crease, 2 cm from the end.
6. Fold this 2 cm strip over the other way and repeat folding the paper back and forth until you have folded the whole sheet. Stretch out the paper slightly and use it as the new roof for the house.
7. Place the plasticine man in the house and test the strength of the roof by placing the third block of wood on the paper roof. The corrugated paper roof is strong enough to support the weight of the wood and the plasticine man is safe.

## Further investigation

Experiment with how strong a triangle is by making different types of shapes and testing their rigidity. Use eight paperclips and four straws of the same length to make a shape with four sides. Hook the eight paperclips together in pairs, then thread each of the straws onto a paperclip. Pick the square up and notice how easily it changes shape. Now try making other shapes with three, five or six sides. Notice how the triangle is the only shape that cannot be pushed into a different shape once it is made.

## What's happening?

Folding the paper makes a series of triangles, called corrugations. The corrugations make the paper more rigid or stiff, which allows the paper to hold up the block of wood.

The angles of a triangle cannot be changed because each angle is fixed by the side opposite it. This makes triangles a strong shape. Therefore the corrugated paper, with its series of triangles, is able to hold a lot more weight than the flat piece of paper.