Technology

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Materials

• 3 long wooden plant sticks
• Popsicle sticks (42 was enough for the mast shown below)
• Mounting putty
• String
• 3 heavy objects

Short explanation

The radio mast you built consists of lots of small triangles. This type of construction is called a truss, and it becomes very stable.

Long explanation

A truss consists of straight bars that are assembled into triangles. When three bars are assembled as a triangle, the shape of the triangle cannot be changed, which makes trusses very stable. This can be compared to four bars assembled as a square - which can be pressed together even if the bars are connected.

In a truss, the nodes, i.e. where the bars are connected, are considered to be movable like hinges. This means that each bar is only exposed to pressure or tension, i.e. forces that either try to shorten them or stretch them longitudinally. There are no forces trying to bend the bars.

What you built here is a mast and not a tower. Engineers usually define the difference between a mast and a tower that a mast is held up by cables or supports, while a tower stands by itself.

A mast is often very unstable without its guyes, which is the name for the cables attached to the ground. In fact, the Warsaw radio mast began to tilt too much and collapsed as a guy was being replaced 1991. With its 646 m (2,121 ft), the radio mast was the world's tallest construction at the time.

Test and improve

You have now built your first prototype. There are probably improvements to be made. In order to keep working on your design, try answering any of the following questions.

• What happens if you build a taller mast?
• What happens if you remove one guy.
• What happens if you attach the guyes to lighter objects?
• What happens if the mast begins to tilt?
• How heavy an object can you place on top of the tower before it collapses?

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