parallel axis theorem
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parallel axis theorem[′par·ə‚lel ¦ak·səs ‚thir·əm]
A theorem which states that the moment of inertia of a body about any given axis is the moment of inertia about a parallel axis through the center of mass, plus the moment of inertia that the body would have about the given axis if all the mass of the body were located at the center of mass. Also known as Steiner's theorem.