关键词: 刚体, 对称面, 转动惯量, 定理, 转轴

Abstract: A new theorem about the moment of inertia of rigid body is proposed and proved.This theorem states that the inertia of a homogeneous rigid body with a symmetry plane is not concerned in any direction of the axis that lie in that plane,when the axis that lie in a plane which be perpendicular to the symmetry plane meet certain conditions.

Key words: rigid body, symmetric plane, moment of inertia, theorem, axis