Free STEM Lesson

Lesson 9: Bridge Engineering

For Grades: K - 6

Step 1 - Introduction


Lesson Overview

Learn about types of bridges and build your own! Can you build a bridge that can support a heavy book?


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Step 2 - Learn More



A beam bridge is a simple bridge made of a sturdy beam that stretches across an area. Sometimes the beam has supports called piers. A beam bridge can bend or break if there is too much weight.


A truss bridge has additional supports called trusses in the shape of triangles. Triangles are a strong shape because pressure on the point of a triangle will spread out the weight and they won’t bend.


An arch bridge includes an arch shape underneath the deck for support. The curved arch spreads the weight across the entire bridge structure.


Suspension bridges use thick steel cables to hold up the bridge using tension. The weight on the bridge pulls on the cables which spread out the weight. Suspension bridges can be built to cross long distances, like the Golden Gate Bridge in San Francisco!

Step 3 - Your Project

For Grades k-6

Challenge Explanation

Watch ms. Westmoreland test out her beam style bridge. Will it hold the weight of this heavy book!

Build a Bridge

The Challenge: Build a bridge that can span 1 foot support the weight of a large book!

  • Materials
    • Something to build your bridge with
      • Ideas: Legos, any building set, or recyclables!
    • Items to build your bridge across
      • Ideas: 2 kitchen chairs, 2 small tables, 2 stacks of books, 2 boxes, etc.
    • Something that weighs about 1 pound
      • Ideas: Hardback book, can of food, wood blocks etc. **For safety, don’t choose anything too heavy! Check with your parents.** 
    • Ruler
  • Set Up
    • If the weather is nice, this is the perfect project to work on OUTSIDE!
    • Measure and arrange your building area. For example, place 2 kitchen chairs 1 foot apart to build your bridge between.
      • For older nerds or those that want an extra challenge, try 18 inches!
  • Use the Engineering Design Process
    • Ask – How can I build a sturdy bridge that will support about 1 pound of weight?
    • Imagine
      • What type of materials will you use?
      • What type of bridge design will you try? (Beam, Truss, Suspension or combination?)
    • Plan
      • Draw out your plan on paper before you begin.
    • Create
      • Build your bridge!
      • Test CAREFULLY by placing the book or weight on your bridge! Make sure if your bridge collapses, the book won’t land on your toes!
    • Improve
      • Did your bridge bend or break? 
      • Can you reinforce it to make it stronger?
      • Do you want to try to span a longer distance, like 2 or 3 feet?!
    • Share – See step 4


Step 4 - Share


Share with someone you love!

Share with someone you love! Today’s recommendation is to call a grandparent (or older family member) that doesn’t live at your house, and tell them about your project!

  • Possible things to talk about:
    • What did you learn?
    • What did you build?
    • What problems did you run into?
    • How did you solve them?

Step 5 - Go Deeper

For Grades K-6

Learn more and try new things!

  • Can you build another bridge out of a different material?
  • What if you combine two bridge design styles into one?
  • There are MANY other bridge designs possible. Ask a parent to help you research online. 

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Nerdy Comments!

Did you enjoy this lesson? Leave a comment here or on our Facebook Page! We would love a picture or video of your project builds and remember to give other nerds out there some words of encouragement!

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