Bridge Building

Science Lesson Plan

Students will build a bridge that can hold as much weight as possible. They will be introduced to several real bridges and to the art of bridge building.

books on building bridges, pictures of bridges of different styles, K'NEX building set (color coded plastic rods & connectors) or straws and straight pins


  1. Create a KWL chart where you can write what your class knows and what they want to know about bridges. The L column is where you will record what they learned once you are done with the activity. Have your students share what they know about bridges. Record the responses in the K column of the KWL chart.
  2. Ask your students what else they would like to know about them. Record their responses in the W column of the KWL chart.
  3. Have plenty of books available on bridges for your class to peruse. In groups, let your kids jot down interesting things that they find out about bridges.
  4. Record some of these findings in the KWL chart.
  5. Tell the class that they will be building a bridge. If using K'NEX you may want to do this as a center activity, as you will most likely not have enough sets for the entire class. If using straws and straight pins, it works well to specify the amounts of each such as 25 straws and 100 straight pins. The object is to build the strongest bridge that can hold the most weight. If using K'NEX, you also may want to add that it needs to be the lightest bridge.
  6. Let them choose the basic design, but have them specify some general criteria; such as length of actual bridge part, distance between ends, etc.
  7. Have them build the bridge in small groups.
  8. After the bridges are finished, have students predict which bridge they think will hold the most weight. Discuss why. In order to test the strength, hang weights from the bridge until it starts to collapse.
  9. EXTENSION: Have your students research famous bridges, bridge incidents, particular aspects of bridge architecture, etc. They can write a report, make a visual aid, and give a presentation to the class.

With class discuss which bridge held the most and why. Have students talk about bridge building, why it needs to be precise, some of the difficulties involved, and what could happen (and has happened) if bridges are not constructed correctly. Write down more things that your class learned about bridges and record in the KWL chart.

Notice the students who didn't contribute during discussion both before and after building the bridges. Who was really involved in the building and designing aspects of the activity? Which groups were able to create a strong, realistic design for their bridge? Notice those students who had trouble following directions.

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