如图所示，我们在拖动行李箱时一般先拉出行李箱上方的拉杆，这样做的目的是为了

下列测量工具没有利用杠杆原理的是（　　）

下列工具在正常使用的过程中，可以看作费力杠杆的是

如图所示，杠杆处于平衡状态，则F的力臂是
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               

使用滑轮组肯定不能做到的是

4、如图所示，甲、乙、丙三个相同的杠杆，所挂的物体受到的重力均为G，它们分别在方向如图所示的力F₁、F₂、F₃作用下处于平衡状态，那么

如图所示，起瓶器开启瓶盖时，可看作是

“给我一个支点和一根足够长的棍，我就能撬起整个地球．”下列生产和生活中的杠杆与阿基米德设想的杠杆属于同一类型的是

如图所示，弹簧测力计A、B和滑轮组组成的装置中，若拉绳的力为F，则两弹簧测力计的示数为(     )   

A．F _A="F" _B = F         B．F _A=3F   F _B ="2" F
C．F _A= 2F  F _B =3F    D．F _A="F" _B=3F/2

如图所示，在竖直向上大小为10N的力F的作用下，重物A沿竖直方向匀速上升。已知重物A上升速度为0.2 m／s，不计滑轮重、绳重及绳与滑轮间的摩擦，则物体的重力大小和滑轮上升的速度分别为(    )