Moment of inertia(惯量) The inertia of the rigid body that is rotating definition J=∑△m,r2 A continuous body: J=Sr2dm the moment of inertia of one rigid body is determined by its shape the position of the axis and the density distribution Moment of inertia（惯量） The inertia of the rigid body that is rotating definition 2 i i J  m r A continuous body: J r dm2   the moment of inertia of one rigid body is determined by its shape , the position of the axis and the density distribution