You can build a miniature catapult from rubber bands and bamboo pieces or pencils. This project is easy enough that a child can build it with a little trial and error. Your catapult can shoot marshmallows, candies, paper balls or other small objects. The design is quite flexible -- you can easily modify the design to work with other basic materials, or make it stronger if you like.
Place two bamboo sticks or pencils on the table, six inches apart and parallel. Place a third pencil atop the other two at a 90-degree angle, near the bottom of the first two pencils, as if making a U. Wrap a rubber band around the intersections of the pencils, securing the top pencil to the bottom two. Wrangle with the design until it makes a nice U shape and the bands are tightly secure.
Place another pencil atop the original bottom two, closing the U into a square. Secure this pencil with rubber bands as you did in step 1. The finished square should have two parallel bottom sticks and two parallel top sticks. Make sure the square is tightly bound by adding more rubber bands, if necessary.
Place two pencils or sticks at the outside right top and bottom edge of the square, as if starting to build a three-dimensional cube. Wrap rubber bands around the intersections of the pencils as you did before. Take a third pencil and place it atop the other two, making a crossbar, again as if part of a three-dimensional cube.
Place one end of a pencil at the front of the top crossbar, dropping the other end of the new pencil down to the left side of the bottom square. Do the same with another pencil at the back end of the crossbar, keeping it parallel to the first pencil in this step. Secure both pencils by wrapping with rubber bands as in the above steps. The end result should look like a right triangle if you looked at it head-on from the front or back. Wiggle all the sticks or pencils and add rubber bands if any are loose.
Place a pencil three-fourths of the way up from the table along the diagonal crossbars. Secure this pencil with rubber bands, keeping it parallel to the table. Make sure this new crossbar is very tightly secured, as it will hold the spoon in place. This completes the catapult frame.
Slide a spoon into the catapult frame, with the open bowl facing right and up. The spoon handle should touch the right-most pencil that rests on the table, and lean up against the crossbar created in Step 4. Wrap rubber bands around the spoon handle attach it to the frame where it touches the table, creating a pivot point. Twist another rubber band so it stretches around the top of the spoon, attaching the band at each end of the crossbar the spoon leans against. (This band will create the flinging power of the catapult if placed properly.) Twist the band as needed to create pulling tension.
Place a small marshmallow or ball of paper in the spoon bowl and pull back on the spoon. Hold the base of the catapult with your other hand. Release the bowl to fire the catapult.
You can easily modify this basic design into a larger, more powerful catapult. Simply use larger sticks (such as broomstick-width dowel rods) and bungee cords or other strong, elastic material. The image in Reference 1 is a good reference if uncertain about construction. Keep extra rubber bands handy to tweak the catapult design as needed.
Do not aim or point the catapult at any person or animal's face. Be sure to keep your own face away from the potential projectile path when working on this project.