2.上述圆环的各质点到z轴的距离都为r,于是 圆盘对轴的转动惯量为: 2M M J2 Mram= rar= REMR R 2R 2 3.圆盘对轴的回转半径为 R IM 23．圆盘对z轴的回转半径为 R M J Z Z 2 2  = = r R R r R M r M M d m d r R R J z M 2 0 3 4 0 2 2 2 2 1 2 2 =  =  = = 2．上述圆环的各质点到z轴的距离都为r,于是 圆盘对z轴的转动惯量为: