Get ready to launch marshmallows across the room with the power of a mousetrap! Print out our Marshmallow Catapult instruction sheet with step-by-step pictures.

SAFETY NOTE: Mousetraps are dangerous! If one snaps back on your hand it could break a finger. This project requires adult permission and supervision.

What You Need:

What You Do:

make your own mousetrap catapult!

  • With a pair of pliers, carefully remove any metal teeth or bait platforms from the trap. Also take out any staples that are not connected to the spring.
  • Carefully pull back the snapper arm until it reaches the other end of the trap, and hold it down firmly. Have a helper wrap the strong rubber band around the end of the snapper until it holds it down to the base of the trap, preventing the trap from springing.
  • Use a loop of duct tape to attach one of the erasers to the base of the trap so its long side is right next to the fulcrum (the spring in the middle of the trap).
  • Tape the second eraser on top of the first one, letting it hang over the fulcrum slightly. Secure both erasers to the base with duct tape, then carefully remove the rubber band and slowly let the snapper arm move up until it rests against the erasers.
  • Tape one of the tongue depressors horizontally along the top of the snapper arm. Place the second tongue depressor perpendicular over the first and tape it so it extends vertically above the snapper arm.
  • Tape the spoon to the second stick.  Make sure that the arm of the catapult will hold.  You may need to reinforce it with more duct tape.
  • To shoot the catapult, take any small soft object, such as a marshmallow, and then pull back the arm, put the object in the spoon, and let go!  Always be sure to hold down the base of the catapult when you release the arm so the structure doesn’t topple over.

What Happened:

Newton’s first law of motion states that objects in motion tend to remain in motion, unless acted on by an outside force. When you released the catapult, both the lever arm and the “ammunition” moved forward with energy from the spring. When the lever arm hit the erasers, it came to a sudden stop. The marshmallow, however, remained in motion until it hit something else or until the force of gravity overcame its motion and brought it to the ground. The same principle applies to driving in a car – both you and the car are moving together, but if the car comes to a sudden stop (as in a collision), your body will keep moving forward. This is why you should always wear a seatbelt!

This project is adapted from BOAST hands-on science lessons.