前后 力比值 上的利 求残线组:Fb=mgq F F mg 2+oh mg bng xb1=9 L Fxb= Fxbl+ Fxb2 Fx21/// b1=2 (Fxbl Fxb2)hg L L L b1 g ng mg b2 bl h h9/16 ( ) g xb g g xb xb xb g xb xb xb xb xb g xb z g xb h mgL F h L h F L F F h L mgL F F F F L F h L mgL L h L mg F F f F mg 2 2 1 2 1 2 1 1 2 2 1 1 2 ( ) − − =         + = + = +         = = + = + =        求 线组：  Fxb1 Fxb2 (0, ) 2 g h mgL −