Cotton Ball Catapult

Objectives

• Understand the concept of action and reaction forces.

Materials

• Per Group:
  metre stick
  cotton balls

• Per Group or per Student:
  1 plastic spoon
  1 ruler
  1 length or roll of masking tape
  2 rubber bands

Key Questions

• What kinds of forces are at work in your catapult?
• How is energy converted and stored by your catapult?

What To Do

1. Challenge students to work individually or in groups to see who can make a cotton ball catapult using only the materials provided.
2. Once students have made their catapults, test them and use the metre stick to measure how far their cotton balls fly.

 

For younger students, a pictorial “How To” might look like:

Step One: Collect Materials

Step 2: Design and Assemble

Step 3: Test

Vocabulary

• potential energy: Energy stored in an object either due to its position (i.e. in relation to the ground) or condition (i.e. stretched or compressed in a spring or elastic band).
• kinetic energy: The energy of a moving object. Potential energy is converted into kinetic energy when an object is acted upon by a force.

Extensions

• Try loading different projectiles into your catapult (such as pompoms and ping-pong balls). Do they go further than the cotton ball? Why or why not? Be careful not to hit anyone with hard objects.
• How does changing the materials (i.e. thicker rubber bands or more flexible spoons) affect the outcome? Explain your results in terms of forces.