To build a ballistic pendulum, use a cardboard box, weights, four eye hooks, nylon string, a piece of plywood and a sheet of white paper. Mount the ballistic pendulum after it is constructed.
- Create the box
Use a box that is 1 foot in width, 1 foot in height and 18 inches in length. Cut a square opening in the front of the box measuring 9 inches tall and 9 inches wide. Attach duct tape to every corner of the box. Crumple a few newspapers, and put them through the box opening. Add weights to the opening that equal exactly 4 pounds.
- Attach the string
Push the eye hooks through all four corners on the top of the box. Attach duct tape around the hooks to secure them. Tie 3-foot strands of nylon string to the loops of the hooks at each corner.
- Secure the marker
Tape a felt-tip marker to the bottom of the box with duct tape. Attach the felt tip to the center of the bottom. Ensure that the tip of the marker protrudes slightly from one side of the box.
- Mount the pendulum
Tie the string holding the box to a secure ceiling fixture. Glue a 4-foot long sheet of paper to a 4-foot long piece of plywood. Mount the plywood at the same height as the box, and push the paper toward the box until it barely touches the marker tip.