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ballistic pendulum

noun, Physics.
a device consisting of a large mass hung from a horizontal bar by two rods, used to measure the velocity of an object, as a bullet, by retaining the object upon impact, its velocity being a function of the displacement of the mass.
1770-80 Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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Examples for ballistic pendulum
  • The projectile strikes a baseball causing it to fly toward a ballistic pendulum.
Encyclopedia Article for ballistic pendulum

device for measuring the velocity of a projectile, such as a bullet. A large wooden block suspended by two cords serves as the pendulum bob. When a bullet is fired into the bob, its momentum is transferred to the bob. The bullet's momentum can be determined from the amplitude of the pendulum swing. The velocity of the bullet, in turn, can be derived from its calculated momentum. The ballistic pendulum was invented by the British mathematician and military engineer Benjamin Robins, who described the device in his major work, New Principles of Gunnery (1742).

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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