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Related to principal axis: centre of curvature
principal axis[′prin·sə·pəl ′ak·səs]
The longest axis in a crystal.
A reference direction for angular coordinates used in describing the directional characteristics of a transducer; it is usually an axis of structural symmetry or the direction of maximum response.
One of a set of perpendicular axes such that a quadratic function can be written as a sum of squares of coordinates referred to these axes.
For a conic, a straight line that passes through the midpoints of all the chords perpendicular to it.
For a quadric surface, the intersection of two principal planes.
One of three perpendicular axes in a rigid body such that the products of inertia about any two of them vanish.
ii. The axis of relative wind.
iii. The principal inertial axis: that line passing through the center of gravity in a plane of symmetry about which a long, slender body tends to rotate when rolling.
iv. A rectilinear axis in the plane of a cross section of a structural member about which the moment of inertia is the maximum.