OL x2)OL m1+ +ox-mg a 2 带入拉氏方程d/aL)a dt( ax Ox 得, 0x+m g 4a 4 2aa x x mg a x m x L a x mx x L 4 2 , 4 1 2 2 2 2 2 − = + = + 带入拉氏方程 0 d d = − x L x L t 得, 0 4 4 2 1 2 2 2 2 2 + = + − + a x x mg a x a x x