Ballistic Pendulum

Ballistic Pendulum, a contrivance designed for the measurement of the speed of projectiles, but which has now given way to other and better arrangements for that purpose. It consists of a heavy, drum-shaped block of wood, suspended by a light rod as with an ordinary pendulum. The projectile, so fired into the block as to avoid jarring the point of suspension, shares its amount of motion with the block, which will therefore start moving with a certain velocity. Observing the displacement of the pendulum from its mid-position, and with a knowledge of the weights of the projectile and block, the velocity of the former may be estimated.