放置克令吊吊臂前,应先将吊臂转到支架上方,再把旋转手柄放在()
A.旋转位置;
B.“零位”空挡位置;
C.刹车位置;
D.松开位置。
参考答案:B
如图所示,物体a、b和c叠放在水平桌面上,水平力Fb=5N,Fc=10N分别作用于物体 b、c上,a、b和c仍保持静止.以Ff1, Ff2,Ff3分别表示a与b,b与c,c与桌面间的静摩擦力的大小,则
A.Ff1=5 N,Ff2 =0,Ff3 =5 N
B.Ff1=5N,Ff2 =5 N,Ff3 =0
C.Ff1=0,Ff2=5 N,Ff3 =5 N
D.Ff1=0,Ff2 =10 N,Ff3 =5 N
As agreed upon in our negotiations, payment ( )L/C.
A.by
B.will be
C.is to be made by
D.is by