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reduced mass[ri′düst ′mas]
a coventional characterization of the distribution of mass in a mechanical or mixed (for example, electromechanical) system in motion. Reduced mass depends on such physical parameters of the system as mass, moment of inertia, and inductance, as well as on the law of the system’s motion. In the simplest cases, the reduced mass μ is defined by T = ½ μv2, where T is the kinetic energy of the system and v is the velocity of a certain characteristic point, to which the mass of the system is being reduced. For example, for a body in plane-parallel motion, μ = [1 + (ρc/hc)2]m relative to the center of mass C, where m is the body’s mass, pc is the radius of inertia relative to the axis perpendicular to the plane of motion through the point C, and hc is the distance from the center of mass to the instantaneous axis of rotation, which as a rule is variable.