How to Build a Shoebox Catapult
The principle behind a shoebox catapult is simple enough that it has been utilized since antiquity. It is a principle that changed warfare, that conquered cities and countries, and that shaped the history of warfare. This simple principle is the transfer of stored energy into a projectile. Whether you need a good science project, a visual aid for your history report or a way to liven up playtime with your child, don't brandish this toy lightly.
Cross two pencils perpendicularly so that the midpoint of each pencil overlaps. Then encircle both pencils around their midpoints with tape until the pencils are bound firmly together.
Place the stem of the spoon under one of the pencils. Wrap the pencil and the spoon's stem with tape until they hold together well. You should now have a cross with one of its arms extended by a spoon; this will be the launching mechanism while the other perpendicular pencil will be the pivot around which this launching mechanism rotates.
Place pencils in the shoebox so that the spoon is oriented lengthwise. The other pencil should be touching the sides of the box. Rotate the pencils until the the spoon is completely upright and the other end of the pencil in which the spoon is attached is millimeters from the bottom of the box.
Mark the two points at which the pivot pencil touches the sides of the shoebox. Use the scissors to pierce holes at these two points. It does not matter if these holes are closer to one end or the other, but typically the holes are situated so that the spoon barely overhangs the lip of the box when it is cocked in the horizontal position.
Run the pivot pencil through those holes, hen pierce two more holes directly below this pencil. These holes should be right where the bottom of the box meets the sides.
Run a pencil through these two holes. This pencil will stop the spoon when it reaches the upright position when the catapult is in use.
Pierce a hole in the bottom of the box about an inch behind that bottom pencil, closer to the spoon side. Run you rubber band halfway through this hole.
Put the last pencil through the loop of the rubber band on the under side of the box. Then wrap it around the end of the pencil to which the spoon is attached.
Place a marshmallow in the spoon and cock it back to a horizontal position. The rubber band should now be stretched out, storing energy. Release the spoon and the spoon should quickly rotate from horizontal to vertical where it will simultaneously be stopped by the pencil on the bottom and transfer its energy into the marshmallow.