23 Feb, 2013
PRESENTATION: A ball that has been thrown at a particular velocity hits a suspended target. The target reaches a certain height after being hit. By measuring this height, the recoil velocity can be calculated using principles of conservation that are well-known in Classical Mechanics.
- An inexpensive, multipurpose physical pendulum, David Schultz, Phys. Teach. 50, 436 (2012)
- So what else can you do with a ballistic pendulum, Robert K. F. Keefer, Phys. Teach. 28, 495 (1990)
- Modifying the ballistic pendulum apparatus, Lee D. Matthews, Phys. Teach. 14, 245 (1976)
INTRODUCTION: The principles of conservation are fundamental to Physics. By using these principles it is possible to study and predict the evolution over time of many systems. The principle of conservation of mechanical energy and that of linear momentum will be used to study the operation of a ballistic pendulum, which makes it possible to measure the speed at which a projectile is shot.
OBJECTIVE: To determine experimentally using a ballistic pendulum the initial velocity of a launched projectile.
MATERIALS: pendulum with stand, launcher, plastic balls, copper weights, chronometer, scales.
SETUP: The pendulum is placed on the edge of a table and firmly fixed. The launcher is attached to the pendulum with a wing-nut in one of the holes in the pendulum designed for this. The pendulum can be placed so that it has an inelastic impact or elastic impact (simply by turning the pendulum), depending on what is needed.
EXPLANATION: An elastic impact is one in which kinetic energy is conserved. The kinetic energy after the impact is converted into potential energy. Once the angle of deviation of the ballistic pendulum is known, we can calculate the bullet’s initial velocity.
If the impact is inelastic, part of the ball’s kinetic energy is passed to the pendulum, another part is used to move the ball and the rest is dissipated as heat.
CONCEPTS: conservation of mechanical energy, conservation of kinetic momentum, conservation of angular momentum, elastic impact, inelastic impact.
- TIPLER, Paul, Física para la Ciencia y la Tecnología, Reverté, 2010.
STUDENTS 2012-2013: Ángel López, José Ignacio Iglesias, Isabel López
LINK pdf STUDENTS (in Spanish):