PURPOSE: To determine the speed of an air gun pellet using a ballistic pendulum.
DESCRIPTION: The pellet from an air gun is shot into a foam-filled can, which acts as the pendulum. Conservation of linear momentum in the inelastic collision determines the speed with which the pendulum receptacle leaves the collision. Conser vation of energy determines how high the pendulum will rise, or alternatively, the maximum angle to which it swings. Working backward, we can determine the velocity v of the pellet: v = [(M + m)/m] SQRT (2gh), where < EM> m is the mass of the pellet, M is the mass of the receptacle can, h is the height to which the can rises, and g is the acceleration of gravity. The height h is determined by measuring the radius R of the pendulum and the horizontal displacement x of the receptacle can after the collision.
For adequate repeatability, pump the gun eight times. Be familiar with the safety mechanism, and know where the pellet exits the gun before firing.
SUGGESTIONS: BE CAREFUL WITH GUN!!!
REFERENCES: (PIRA 1M40.40) See Demonstration Reference File for detailed derivation of the equations used for this particular apparatus, as well as sample data.
EQUIPMENT: Pre-assembled ballistic pendulum apparatus, air gun with pellets.
SETUP TIME: 5 min.
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