Brief Description:

Students will design and build a catapult and see which design will launch an object the furthest.

Grades: 3, 4, 5, 6, 7, 8

Time: 2 hours

Keywords: lego, simple machines, levers, catapults

Lesson Objectives

  • Students will learn about and be able to identify the three classes of levers
  • Students will use this knowledge to build catapults


  • Legos
  • For catapults
    • Popsicle sticks
    • Spoons
    • Rubber bands
    • Tape
    • Paper


Day 1:

  1. Discuss Levers.
    1. A lever is a simple machine that makes work easier for use; it involves moving a load around a pivot (or fulcrum) using a force
    2. Class I Lever
      1. Examples: hammer, scissors, seesaw
    3. Class II Lever
      1. Examples: Nail clippers, wheel barrow
    4. Class III Lever
      1. Examples: Tweezers, fishing rod


  1. Have students construct one of each lever using Legos.
    1. Use a weighted brick or other items found around the classroom as the load. Place this at one end of the lever.
    2. Students will lift the load by applying effort to the opposite end of the lever.
  2. Let students experiment with the placement of the fulcrum, load, and effort.
  3. Bring the class together and discuss how students were able to lift a load with the least amount of effort. Ask:
    1. What conditions made it easiest to lift your load?
    2. What building difficulties did you come across?
  4. Clean up. Continue with levers in the following class period.

Day 2

  1. Review types of levers.
  2. Challenge students to build a catapult out of the provided materials.  A catapult is a projectile device used to launch a an object a great distance without the aid of explosive devices. They work with the use of levers.
  3. Allow the class to brainstorm different ideas for their catapult design. Have them plan out and draw their design on the engineering planning sheet.
  4. Distribute materials and have students start building.
  5. After students finish building their catapults, have them place their catapult on the line and launch an lego/small object (preferably something that will not roll). Measure how far the catapult launched the object.
  6. After all of the students have presented, review the activity with the class. What worked well? What didn’t work? What type of lever was your catapult?


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