Which shape is more stable, a triangle, square or pentagon?

Materials: Cycle valve tube (1 cm pieces) and matchsticks with blackheads cut off.

Make a Prediction
Draw which shape you think will be more stable. Why do you think so?

Try It Out
1. Build a triangle, a square and a pentagon with the matchsticks and cycle valve tubes .
 2. Compare the stability of the shapes. Stand each shape up and press down on the top corner. What happens? How much does each one bend and twist? How hard can you press down on each shape before it collapses?

Draw the shapes that you get when you bend a triangle, a square and a pentagon.

Explain It
Compare the results of your tests.

Which shape was more stable?

What do you think made it more stable?

How might this shape be used in large structures? 

Did You Know

Truss is a skeleton-like structure composed of struts (short straight pieces), joined to form a series of triangles.

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