Play Catapult

Catapults are launching devices that have been used since the medieval era to launch everything from rocks to people to eggs. Regardless of the size of the catapult or the object being launched, the basic principles are the same: an object is placed on the end of a catapult arm and propelled into the air by the arm's movement. If you wish to build a simple, small sized catapult that can launch a hacky sack, you can do so in a few simple steps.

Instructions

Assembling the Frame

1 Cut three 12-inch pieces out of the 3/4-inch by 1/2-inch wood strips. Cut an additional seven 6-inch pieces out of the wood strips and use a protractor to cut the ends of two of these strips at a 45 degree angle.
2 Line one of the wood pieces with the angled edges up with one of the 12-inch pieces so that the two wood pieces form a 45 degree angle. The angled portion of the 6 -inch wood piece should be flush with the bottom edge of the 12-inch wood piece and positioned all the way at one end of the 12-inch wood piece. Secure the wood pieces together with wood glue and a 3/4 inch wood screw.
3 Place a non-angled 6-inch wood piece so that its edge is flush with the remaining angled end of the 6-inch wood piece you secured in Step 2 and its bottom end is flush with the bottom edge of the 12-inch wood piece it is secured to. Secure this 6-inch wood piece to both the 12-inch piece and the angled 6-inch piece with wood glue and 3/4-inch wood screws. This assembled piece will serve as the side support for the catapult.
4 Repeat Steps 2 and 3 to create another side support for the catapult.
5 Stand the two side supports side by side exactly 6 inches apart. Connect them together by placing two 6-inch wood pieces on the front (the end closest to the uprights) and back end of the side supports and securing them in place with wood glue and 3/4-inch wood screws. You will now have a rectangular frame that measures 6 inches by 12 inches.
6 Place the final 6-inch wood piece across the top of the frame's two uprights. Secure it in place with wood glue and 3/4-inch wood screws. This cross beam will stop the catapult arm when it is in motion and cause the catapult to launch the hacky sack.
7 Drill a 2mm hole through the sides of the frame's two uprights. Position the hole near the base of the uprights to allow the catapult arm full range of motion. Screw an eye-hook into the middle of the frame's front beam to finish the catapult frame.

Assembling the Arm

8 Cut off the top of a paper cup to create a small basket for the arm of the catapult. Screw the basket to the end of the remaining 12-inch wood piece with a 1/2 inch wood screw.
9 Screw a second eye-hook into the catapult arm directly below the paper cup you secured in Step 1.
10 Drill a hole through the side of the catapult arm at the opposite end with a 2-mm drill bit.

Assembling and using the Catapult

11 Cut an 8-inch section of wire clothes hanger. Insert the wire through the hole at the base of one upright, through the hole at the end of the catapult arm and finally through the hole at the base of the opposite upright (make sure the catapult basket is facing up when you do so). Bend the ends of the wire to hold the wire in place.
12 Attach one end of the rubber band to the eye-hook screwed into the catapult arm and the other end to the eye-hook screwed into the catapult frame.
13 Place the hacky sack in the catapult basket, pull back the catapult arm and release to launch the hacky sack into the air.