Strong Shape

Have you ever wondered how architects, engineers and scientists can design buildings, bridges and other structures that can carry huge loads of cars, or people? This month we will take a look at how shape can make a simple object strong.

Most people would say a piece of paper is not very strong. Take a heavy book and four sheets of paper. Can you think of a way to use the paper to hold the book at least 6 inches (15 cm) above a table or the floor? Try it.

Did you do it? Were you able to hold the book up with 4 pieces of paper? Think about it some more. Can you come up with another way to try to do it?

See, you are learning. Most designs take time and a number of tries before you are successful. 

Straws can be used to model building materials. A single plastic straw is very rigid from end to end, like a column, but is not very strong from side to side. Hold a straw at the ends and try to bend it. Pretty easy isn’t it? Now take a handful of straws and fasten them together with a band of masking tape or clear plastic tape at each end. Try to bend the bundled straws. Was this harder? 

You can build with straws. Get 18 plastic straws and a box of paperclips. Open a paperclip into an S shape. Use it to connect 2 straws. You can put a second paperclip into the end of a straw and connect 3 straws together. Use 12 straws to build a box shape. Use another 6 straws to build a pyramid shape. Which do you think is stronger? Use an S shape paperclip and hang a paper cup from the top of each shape. How many pennies can you put into the cup before the shape collapses?

Bridges come in all sorts of shapes and sizes. Stack books up to make 2 piles about 4 inches (10 cm) high and about 6 inches (15 cm) apart. Put a piece of paper from one pile of books to the other. How many pennies do you think the paper will hold before it bends or before the ends of the paper start to lift up? Try it and find out. Now take another piece of paper and use it to make an arch between the piles of books. Put a piece of paper on top as a bridge floor. Make sure the bridge rests on the arch. Do you think this can hold more coins before it bends or lifts up? Try it.

What do you think, do some shapes seem stronger than others?
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