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如图所示,在倾角为θ的斜面上,轻质弹簧一端与斜面底端固定,另一端与质量为M的平板A连接,一个质量为m的物体B靠在平板的右侧,A、B与斜面的动摩擦因数均为μ.开始时用手按住物体B使弹簧处于压缩状态,现放手,使A和B一起沿斜面向上运动距离L时,A和B达到最大速度v.则以下说法正确的是(   )

A:A和B达到最大速度v时,弹簧是自然长度

B:若运动过程中A和B能够分离,则A和B恰好分离时,二者加速度大小均为g(sinθ+μcosθ )

C:从释放到A和B达到最大速度v的过程中.弹簧对A所做的功等于 12 mv2+MgLsinθ+μMgLcosθ

D:从释放到A和B达到最大速度v的过程中,B受到的合力对它做的功大于 12 mv2

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B

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