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Forces and Shapes
Strong shapes are used when people design buildings. These shapes make buildings that can withstand the forces that act on them. Three strong shapes are often used in buildings. These shapes are rectangles, arches, and triangles.
In the diagrams below, the pairs of arrows show the following forces at work:
<– –> tension –> <– compression
A rectangle can be quite strong. But it is not as strong when a force pushes on one of the vertical sides. Its shape can change, making it weaker. Builders add a diagonal support piece to make the rectangle stronger. This support piece is called a brace. It goes between two opposite corners of the rectangle.
An arch is a strong shape. But it is not as strong when a force pushes down on the top of the arch. When a force pushes down on the top of the arch, the sides of the arch spread outward. To make an arch stronger, builders add supports on each side. These supports are called buttresses. The buttresses prevent the sides of the arch from spreading outward.
A triangle can be a very strong shape. If a force pushes on the top point, the triangle is very strong. But if a force pushes on the side of a triangle, the side can bend.
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1. Match the definition to its correct term.
It goes between two opposite corners of the rectangle
prevent the sides of the arch from spreading outward
2. Match if the statement is true or false.
- Three strong shapes often used in buildings are rectangles, arches, and triangles.
- Strong shapes do not make buildings that can withstand the forces that act on them.
3. A pushing force is applied to the side of a rectangle. What internal force acts on the brace?CorrectIncorrect
4. A force pushes down on the top point of a triangle.
What internal force acts on the two sloping sides of a triangle?CorrectIncorrect
5. A force pushes down on the top point of a triangle.
What internal force acts on the bottom of the triangle?CorrectIncorrect
6. What two shapes are used to build an igloo?CorrectIncorrect
7. Which roof would be safer for a house built in an area that gets a lot of snow: a triangular roof or a flat roof?CorrectIncorrect