Table of Mechanics Demonstration List of Mechanics Equipment & Supplies Lecture Demonstrations

# Ballistic Pendulum, 1M40.40

Topic and Concept:

Location:

Abstract:

A safer variation on the standard ballistic pendulum consists of a ball baring launched from a spring-loaded launcher into a bifilar-suspended catcher showing the conservation of energy.

 Equipment Location ID Number Ballistic Pendulum Apparatus ME, Bay B10, Shelf #1

Important Setup Notes:

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Setup and Procedure:

1. After placing the apparatus on the bench top, use the three set screws and mass suspended over the protractor (see photos) to level it.
2. There is hole in the ball baring. Place the baring on the launcher by putting the launching rod through this hole.
3. Cock the firing mechanism by pushing on the baring horizontally, opposite to the catcher.
4. There is a release lever situated on the top of the housing of the launcher. When ready to launch the baring, push downward on this lever.
5. Using the part specifications below, and a careful measurement of the angular displacement, one can calculate the energy dissipated into the catcher.

Cautions, Warnings, or Safety Concerns:

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Discussion: The catcher and the ball baring have a mass of 314.8 g and 57.3 g respectively. On average, an angular displacement of about 18.5° is observed. An estimate of the initial kinetic (total) energy of the ball baring can be obtained if the initial velocity is known. Through slow motion video analysis, we obtained an average initial velocity of 17.7 m/s. Thus, the ball baring has an energy of (1/2) * 0.0573 kg * (17.7 m/s)2 = 8.98 J. Note that the effective spring constant, taking friction into account is about 31.7 N/m (derived from the slow motion analysis; the actual spring constant is about 1262 N/m +/-90). The length of each bifilar support to the center of the catcher is about 32.7 cm.

Videos:

References:

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