How to Build a Catapult With an Electronic Trigger

Construct the Catapult

• 1

  Bend one end of a metal strip up to form a hook shape. Place the wood block on the table. Hold the metal strip vertically so the hook is at the top and bent toward you. Place the unbent end of the metal strip on the block near the edge closest to you.

• 2

  Hammer a nail through the strip at one end into the wood. Hammer a nail through the strip at the other end into the wood.

• 3

  Turn the block around. Pull the hooked end of the strip toward you until it touches the wood. Make a dot with a pencil where the strip touches the wood. Release the strip.

Electromagnet Switch

• 4

  Measure 24 inches of wire from the wire spool. Cut the spool at the 24-inch mark with a wire cutter. Measure 8 inches from an end of the wire and make a dot with a pencil. Measure another 8 inches on the wire and make another dot.

• 5

  Wrap the wire around the head of the nail at the 8-inch mark closest to one end of the wire. Wind the wire down to the point and back up again until you come to the other mark on the wire. Wrap strips of cellophane tape around the nail to hold the wire in place.

• 6

  Strip 1/2 inch of insulation from each end of the wire with a wire stripper.

• 7

  Apply a line of bonding glue to one side of the nail. Place the nail horizontally on the block against the dot that was made on it. Hold the nail against the block for a minute before letting go. Let the glue set overnight.

• 8

  Wad a piece of paper into a ball. Place your catapult on the floor with the end that has the nail glued to it facing you. Place a battery on its side next to the catapult.

• 9

  Tape the end of one of the wires to the bottom contact on the battery with a strip of cellophane tape. Tape the end of the other wire to one of the two contacts on the electronic switch.

• 10

  Measure 10 inches from the end of the wire spool. Cut the wire at the 10-inch mark with the wire cutter. Strip 1/2-inch from each end of the wire with the wire stripper. Tape one of the two ends of the wire to the top of the battery with a strip of cellophane tape. Tape the other end of the wire to the other contact on the electronic switch.

• 11

  Pull the metal strip toward you with your other hand. Press the end of the strip against the nail. Release the strip. Place the wadded up paper ball in the hook on the strip. Press the button on the switch to deactivate the electromagnet and release the strip so it can shoot the ball from your catapult.