Shapes Of Structures

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STEM 101

SHAPES OF STRUCTURES
What shapes are the strongest?

Squares/Triangles/Tubes


If you make a marshmallow structure using toothpicks in the shape of a triangle and then try pushing the sides together, what you will discover is that they resist. If you make a square shape with the same materials, they collapse when you push on the sides. You can make the square shape stronger by "bracing the sides", in other words, putting a diagonal stick from corner to corner in the square. If you study the shapes created, you will note that you have made two triangles. You indeed have created what we call a "truss". You will see trusses in many things. Roofs of buildings are one example. Triangles are the strongest shape. Another very strong shape is a tube. If you roll a piece of paper into a tube shape it is stronger than when it is flat.


What is a Truss?


Trusses are used in many structures. They are used in roofs, bridges and buildings. Beam bridges, for example, can span a greater distance with a thicker beam. But there is a limit to the thickness, too thick a beam will no doubt sag and may end up in a river. An alternate solution is to build a beam of triangles, a "truss," which is much lighter than a beam of similar thickness. A bridge with a truss is extremely strong and stable.

 

Does the materials used make a difference in the strength of buildings and bridges?

 

Shape is very important for strength, but so is the material used in construction. A steel beam will hold more weight that a wooden beam of the same size and shape. Bridges are often built of steel and reinforced concrete because they are strong materials.

 

Misconceptions

 

  • A shape can only look one way. Young children can become stuck on the idea that a shape is only a shape if it looks the same. For example, they may believe that a triangle with the point down is not a triangle, or that a long skinny rectangle and a shorter fat rectangle cannot both be rectangles. You can avoid this misconception by having many different types of the same shapes and talking about similarities and differences. When asking children to identify a shape, ask them to tell you how they know what the shape is.

Fascinating Facts

  • Silicon Chips contain silicon - a material found in sand. Silicon is purified and made into a three-foot long crystal. The crystal is then cut into tiny wafers with a diamond-tipped saw. these wafers are then polished to perfection. Chips are then photo-etched onto a wafer. The chips are used in many products, including wristwatches and computers.
  • In 1839, Charles Goodyear accidentally dropped a lump of rubber and sulfur onto a hot stove.  Instead of melting, the rubber charred. It remained flexible even when put in a cold environment. this led Goodyear to invent a process for making products from rubber. Before Goodyear's discovery, there were few uses for rubber.
  • A skilled igloo builder can build an igloo in 45 minutes. Afterwards, the builder holds a lantern against the igloo both inside and outside. AS the snow melts, the moisture that is drawn out freezes. Such an igloo is so well insulated that a person can sit inside without a coat - even when the outside temperature is -500 F.

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