Untitled Document

Procedures

In order to test the hypothesis, it is appropriate to create my own ballistic pendulum. Due to safety precautions, the experiment must be done outdoors, using an air rifle. To test the amount of velocity lost due to air friction, the data gathered from the experiment will be used to calculate a muzzle velocity. While this calculated number is not the actual muzzle velocity, the fluctuation in this calculated number should show us the amount of velocity lost due to air resistance.
By measuring the horizontal displacement of the pendulum, I should then be able to calculate the vertical displacement. The horizontal displacement is measured at the center of gravity, which also marks the radius of the pendulum. By measuring the horizontal displacement, I can use the Pythagorean Theorem to find the horizontal displacement, which I can then use to calculate the muzzle velocity. In order to measure this horizontal displacement, however, a digital camcorder will be necessary. The better frame rate on the camera, the better, as the accuracy of this measurement depends on the accuracy of the film.

Materials needed
A stick (diameter should be no wider than the diameter of a straw), a cardboard box measuring 3 x 5 x 1 inch filled with toilet paper, a nail at least 1 inch long, a plastic straw, air rifle, ammunition, tape measure, a deck, video camera..

1. Drill a hole large enough for the stick into the 3 x 1 side of the cardboard box. Attempt to maintain the boxes center of gravity, by centering the stick on the 3 x 1 side.
2. Insert the stick into the hole, and hot-glue the stick immediately above the hole to ensure the box will stay on.
3. Find the center of gravity on the pendulum (lengthwise). Mark this line with a marker. Measure the distance from the top of the stick to the center of gravity, and record as radius. Mass the pendulum. Mass one piece of ammunition.
4. Cut a 1.5 cm piece of straw, and put it on top of the stick so that it hugs tightly around the stick. Leave approximately .75 cm of the straw off the stick.
5. Using the nail, poke a hole through the straw on top of the stick.
6. Nail the apparatus to the railing of your deck.
7. Fire the air rifle at the target, with the muzzle 1 meter away. Use a video camera in order to measure the longest horizontal distance that the target swings. Record the data.
8. Repeat 5 times for each distance, for 1, 2, 3, 4, and 5.3 meters away from target.