(2)the paralle-axis theorem(平行轴原理) the moment of inertia when the axis is through the center of mass is J.,and the moment of inertia J,about a parallel axis a distance d away is: J.=J。+md For example: mR2 J=mR+mR爬mR2 m R Jz （2）the parallel-axis theorem（平行轴原理） the moment of inertia when the axis is through the center of mass is Jc，and the moment of inertia Jz about a parallel axis a distance d away is: 2 J J md z  c  Jc 2 2 1 Jc  mR 2 2 2 1 Jz  mR  mR 2 2 3  mR For example: