3)设(xy)为合力作用线上一点,将合力作 用于此点,则合力对原点的矩 M=M(F)=x8-yF=x∑F-y∑F 2355=x(-670.1)-y(2329) 70.840 670.1x+2329y-2355=0 ∑F2=232.9N F8∑F=-670N ∑M(F)=-2355N·m(3) 设(x,y)为合力作用线上一点，将合力作 用于此点，则合力对原点的矩： o = o ( R ) = Ry − Rx =  y − Fx M M F x F yF x F y −2355 = x(−670.1)− y(232.9) 670.1x + 232.9y − 2355 = 0 O C FR FRx FRy x (x,y) 70.84o F F . k N F F . k N y ' Ry x ' Rx 670 1 232 9 = = − = =   Mo = Mo (F) = −2355 k N • m