How to Build a Catapult for a School Project
Building a catapult for a school project is a fun way to explore history and physics. There are many different types of catapult you can make, from a plastic spoon taped to a mousetrap to a three-foot trebuchet. The version here is a medium-sized catapult powered by a rubber band, and is meant to be built using materials you can find around the house 2. It requires some cutting, gluing, and nailing, so ask an adult for help.
Break the yardstick into two even halves. To ensure a neat break, score the yardstick across its width using a utility knife. Set one half aside. Break the other half into three pieces. One piece should be four inches long, or as long as your board is wide, while the other two pieces are equal halves of the remaining length.
Stand the two equal pieces of yardstick vertically and glue to either side of the board, about a third of the way down from one end. Glue the remaining piece across the top of these uprights as a crosspiece, forming a square frame.
Glue one side of the cabinet hinge to the end of the remaining length of yardstick. Nail the other side of the hinge to the board just below the square frame.
Screw one of the screw hooks into the yardstick about halfway down its length. Screw the other screw hook into the very end of the board, in line with the hinge and standing upright.
Attach the two hooks using a large rubber band. The rubber band should lay over the top of the square frame. It should be tight enough to pull the yardstick up against the square frame, but loose enough that the yardstick may be pulled back flat against the board.
Glue the lid from an aerosol can to the end of the yardstick so that it faces upward when the arm is pulled back. When you are ready to fire the catapult, place a projectile in the lid, pull the arm back, and release it 2.
For a more powerful catapult, use heavier boards and substitute a bicycle's inner tube for the rubber band.
A catapult, even a small one, can be dangerous. Never fire the catapult at a person or animal.
- Andres Arango/Demand Media