Cotton Catapult – Research-Backed At-Home Activities – Bay Area Discovery Museum

Cotton Catapult

Building a machine like a catapult from start to finish takes children through the entire design process, from thinking about a problem they want to solve to testing out their final product. Along the way, they’ll practice prototyping various solutions and trying out multiple ideas.

Learning Goals

  • Make thoughtful decisions
  • Build STEM knowledge

Materials Needed

  • Materials for making a catapult, such as:
    • Cardboard strips
    • Rubber bands
    •  Plastic spoons
    • String
    • Pipe cleaners
    • Popsicle sticks
  • Cotton balls
  • Pictures of catapults
  • Tape (optional)


  • Look at pictures of catapults from the internet or books and talk about each of the different parts you can see that make up the catapult.
  • Before children start designing, ask them to think about how much force it will take for them to launch a cotton ball, and which of the available materials would be best for replicating the part of the catapult they saw in the photos.
  • Have children design and construct a catapult, and talk to them about what they’re doing. Introduce the idea of trial-and-error, and have them test their catapult by launching cotton balls.
    • If you want, you can use tape to mark lines on the floor to try to hit or pass with the cotton balls.
  • After the first test, prompt children to think about what they can improve and to experiment by making changes to their catapult’s construction and then trying it again.

Tips for Adults

  • Let children design and redesign the catapult as many times as they want. As they swap out or adjust the materials, encourage them to notice which design resulted in the farthest cotton ball launch. Ask them why they think these materials had this result.
  • To measure how far the cotton ball launches each time you can use a ruler or measuring tape, or you can introduce non-standard measurements. For example, try counting how many steps it takes you to get from the starting line to where the cotton ball landed.
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