Center of Percussion


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center of percussion

[′sen·tər əv pər′kəsh·ən]
(mechanics)
If a rigid body, free to move in a plane, is struck a blow at a point O, and the line of force is perpendicular to the line from O to the center of mass, then the initial motion of the body is a rotation about the center of percussion relative to O; it can be shown to coincide with the center of oscillation relative to O.

Center of Percussion

 

a point on a body with a fixed axis of rotation, located such that an impulse applied at this point in a direction perpendicular to the plane passing through the body’s axis of rotation and center of mass is not transmitted to the axis and does not produce an impulsive reaction at the original point of suspension.

A center of percussion always exists on a body that has a plane of symmetry perpendicular to the axis of rotation; the center of percussion lies in the plane of symmetry at a distance of h = I/Ma from the axis of rotation, where M is the mass of the body, I is the body’s moment of inertia with respect to the axis of rotation, and a is the distance between the body’s center of mass and axis of rotation. Rotating percussive devices, such as pendulum-type impact testers and the hammers of hunting rifles, are designed so that the point at which the impulse is applied is the center of percussion with respect to the axis of rotation.

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