题干

 (2011年金丽衢十二校联考)如图所示,光滑水平面上放置质量分别为m、2m和3m的三个木块,其中质量为2m和3m的木块间用一不可伸长的轻绳相连,轻绳能承受的最大拉力为FT.现用水平拉力F拉质量为3m的木块,使三个木块以同一加速度运动,则以下说法正确的是(  )

A:质量为2m的木块受到四个力的作用

B:当F逐渐增大到FT时,轻绳刚好被拉断

C:当F逐渐增大到1.5FT时,轻绳还不会被拉断

D:轻绳刚要被拉断时,质量为m和2m的木块间的摩擦力为FT

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答案(点此获取答案解析)

C

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