Center of percussion

Center Cen"ter, n. [F. centre, fr. L. centrum, fr. round which a circle is described, fr. ? to prick, goad.] 1. A point equally distant from the extremities of a line, figure, or body, or from all parts of the circumference of a circle; the middle point or place. [1913 Webster]

2. The middle or central portion of anything. [1913 Webster]

3. A principal or important point of concentration; the nucleus around which things are gathered or to which they tend; an object of attention, action, or force; as, a center of attaction. [1913 Webster]

4. The earth. [Obs.] --Shak. [1913 Webster]

5. Those members of a legislative assembly (as in France) who support the existing government. They sit in the middle of the legislative chamber, opposite the presiding officer, between the conservatives or monarchists, who sit on the right of the speaker, and the radicals or advanced republicans who occupy the seats on his left, See {Right}, and {Left}. [1913 Webster]

6. (Arch.) A temporary structure upon which the materials of a vault or arch are supported in position until the work becomes self-supporting. [1913 Webster]

7. (Mech.) (a) One of the two conical steel pins, in a lathe, etc., upon which the work is held, and about which it revolves. (b) A conical recess, or indentation, in the end of a shaft or other work, to receive the point of a center, on which the work can turn, as in a lathe. [1913 Webster]

Note: In a lathe the

{live center} is in the spindle of the head stock; the

{dead center} is on the tail stock.

{Planer centers} are stocks carrying centers, when the object to be planed must be turned on its axis. [1913 Webster]

{Center of an army}, the body or troops occupying the place in the line between the wings.

{Center of a curve} or {Center of a surface} (Geom.) (a) A point such that every line drawn through the point and terminated by the curve or surface is bisected at the point. (b) The fixed point of reference in polar co["o]rdinates. See {Co["o]rdinates}.

{Center of curvature of a curve} (Geom.), the center of that circle which has at any given point of the curve closer contact with the curve than has any other circle whatever. See {Circle}.

{Center of a fleet}, the division or column between the van and rear, or between the weather division and the lee.

{Center of gravity} (Mech.), that point of a body about which all its parts can be balanced, or which being supported, the whole body will remain at rest, though acted upon by gravity.

{Center of gyration} (Mech.), that point in a rotating body at which the whole mass might be concentrated (theoretically) without altering the resistance of the intertia of the body to angular acceleration or retardation.

{Center of inertia} (Mech.), the center of gravity of a body or system of bodies.

{Center of motion}, the point which remains at rest, while all the other parts of a body move round it.

{Center of oscillation}, the point at which, if the whole matter of a suspended body were collected, the time of oscillation would be the same as it is in the actual form and state of the body.

{Center of percussion}, that point in a body moving about a fixed axis at which it may strike an obstacle without communicating a shock to the axis.

{Center of pressure} (Hydros.), that point in a surface pressed by a fluid, at which, if a force equal to the whole pressure and in the same line be applied in a contrary direction, it will balance or counteract the whole pressure of the fluid. [1913 Webster]