h=100mL=1000m dF=lpo+pg(h-ylldy dF对通过点Q的轴的力矩h dm= vdF dM=lPo+pg(h-y)lldy M=yPo+ pg(h-y)]Ldy =poLh+-gplh 2 6 代入数据,得 M=2.14×102N.mdM = ydF dM y[ p g(h y)]Ldy = 0 +  − 2 3 0 6 1 2 1 = p Lh + gLh  = + − h M y p g h y L y 0 [ 0  ( )] d 代入数据，得 2.14 10 N m 12 M =   F 对通过点 Q 的轴的力矩  d y O Q h y dy F  d dF [ p g(h y)]Ldy = 0 +  − h =100m L =1000m