Strongest Shapes (Student Instruction)

Experimenting with shapes such as triangles and arches, teams consider which can best support a load without collapsing. They then use index cards and their shape of choice to build a bridge that will support a die-cast toy car.


STEM careers

Grade level


  • 10 or more 3″ x 5″ index cards
  • 1 roll of tape
  • A small object for your structure to support (e.g. a toy car, a few blocks)


  1. Identify the Problem and Constraints
    • How can you build your structure so it can hold a load and not fall down?
      • The load is the weight your structure must support.
    • An engineering constraint is a limitation on your design. There is one constraint for this challenge:
      • While you can use tape to hold your index cards together, you can’t tape your structure to the table or floor.
  2. Brainstorm Designs
    • Spend a few minutes exploring different shapes you can make with your index cards. Try making a square, a triangle, and maybe even an arch.
    • Which shape is the strongest? Find out by pushing down on them and rocking them side to side. Make sure to stand the shapes upright!
  3. Build and Test
    • Use your strongest shapes to start building a structure that can hold a load while standing up.
    • When you are ready to test, place your small object on top of your structure. What happens?
      • Can you add more weight?
      • Did it collapse?
    • If it falls down, no worries. Engineers learn from what isn’t working all the time.
  4. Evaluate and redesign
    • What worked and what didn’t? Think about any changes you would like to make. Ask yourself:
      • How can tape make your structure stronger?
      • What would happen if you doubled up the index cards?
  5. Make Changes and Try Again!
    • Try to make your structure even stronger.
    • Or use the shapes in your design to build a bridge that can hold several objects at once.
  6. Share Your Results with a teacher, parent/guardian, or DiscoverE!


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