A:215
B:1 35
C:116
D:118
— Though Mike is _______ boy, he can say many words.
— How clever!
如图所示,一根均匀的细木棒OC,OA= 14 OC,B为OC的中点,在C点施力将挂在A点的重为180N的物体匀速提升0.2m,木棒的机械效率为90%,这里的木棒是一种简单机械,称为____,提升该物体做的有用功是____J,木棒重为____N(不计摩擦).