题干

关于力对物体做功,如下说法正确的是(   )

A:滑动摩擦力对物体一定做负功

B:静摩擦力对物体可能做正功

C:作用力的功与反作用力的功其代数和一定为零

D:合外力对物体不做功,物体一定处于平衡状态

上一题 下一题 0.0难度 选择题 更新时间:2020-03-14 11:40:49

答案(点此获取答案解析)

B

同类题2

阅读下文,完成各题。

土地

大地

                                                                                           亿万年的静止,此刻在眼里

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                                                                                           祖辈们和树木花草

                                                                                           一起扎根

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                                                                                           繁衍


                                                                                           父母,是一段

                                                                                           枯老的树干

                                                                                           我就是那横出的新枝

                                                                                           站在父母的肩上

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                                                                                           我用嫩叶为帆远航


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                                                                                           土地的深处