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Graphs of Quadratic Functions in Intercept Form

Parabola vertices and x-intercepts

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Practice Graphs of Quadratic Functions in Intercept Form
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Suspended by a Cable

Credit: Leonardo Pallotta
Source: http://www.flickr.com/photos/83265757@N00/73471268/
License: CC BY-NC 3.0

Did you know that the Golden Gate Bridge in San Francisco, California has over 80,000 miles of wire in its structure? That's enough wire to run from Washington, D.C. to Los Angeles, California 30 times!

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Unlike other bridges, a suspension bridge actually suspends or hangs the road using huge cables. Don't worry! The cables are wrapped over large towers and connect to anchors at either end of the bridge. This delicate balance of strength and precision is not easy to achieve, and in fact, architects and structural engineers use parabolas to help construct these bridges.

Credit: Laura Guerin
Source: CK-12 Foundation
License: CC BY-NC 3.0

Look at the distinctive shape of the suspension cables. Their parabolic shape helps ensure that the bridge stays up and that the cables can sustain the weight of hundreds of cars and trucks each hour. Both gravity and compression/tension forces create the curve seen in the cables of suspension bridges. The parabolic cables effectively distribute the weight of the bridge and transfer the compression forces to the towers to which the cables are attached.

See for yourself: https://www.youtube.com/watch?v=GXbdK2HmZ-g 

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Watch the video below to learn more about how suspension bridges work.


  1. Who invented the technique used to make suspension bridges?
  2. What factors need to be considered when building suspension bridges?
  3. How do the parabolically shaped cables help to hold up the bridge?

Image Attributions

  1. [1]^ Credit: Leonardo Pallotta; Source: http://www.flickr.com/photos/83265757@N00/73471268/; License: CC BY-NC 3.0
  2. [2]^ Credit: Laura Guerin; Source: CK-12 Foundation; License: CC BY-NC 3.0


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