Cut a 9-by-9-inch hole in one of the short ends of the cardboard box. Place duct tape across each corner of the box to strengthen it.
Place the corrugated-cardboard box on the scale and fill it with rocks until the scale reads exactly 4 lbs. Fill the remaining portion of the box with crumpled newspaper to act as a cushion when the box is struck by the projectile.
Secure one eye-hook in the top of each corner of the box in such a way that the eye-hooks will hold the box upright and steady. Cut the string into four 3-foot lengths and tie one to each eye-hook.
Poke a hole in one long side of the box large enough to push the felt-tip marker through but small enough to hold it firmly.
Tape the 4-by-4-foot sheet of white paper to the 4-by-4-inch plywood or thin cardboard, covering it completely. Mount the plywood or thin cardboard to a vertical surface, such as the studs inside of an unfinished garage. Hang the box from a horizontal surface, such as the rafters inside an unfinished garage, so that the felt-tip marker just reaches the paper when the box hangs steadily. You can adjust the marker as needed by pushing it farther in or out of the hole in the box.
Things You Will Need
- 12-by-12-by-18-inch corrugated-cardboard box
- Duct tape
- Felt-tip marker
- 4-by-4-foot piece of plywood or thin cardboard
- 4-by-4-foot piece of white paper
- To determine the velocity of a projectile, multiply the vertical rise of the box (measured in inches) by 43.9 and find the square root of the answer. Then divide 4 by the weight of the projectile (in pounds) and add 1. Multiply the two answers, and the velocity will be determined in miles per hour.