试题与答案

如图所示,质量m=10 kg和M=20 kg的两物块叠放在光滑水平面上,其中物块

题型:选择题

题目:

如图所示,质量m=10 kg和M=20 kg的两物块叠放在光滑水平面上,其中物块m通过处于水平方向的轻弹簧与竖直墙壁相连,初始时刻,弹簧处于原长状态,弹簧的劲度系数k=250 N/m。现用水平力F作用在物块M上,使其缓慢地向墙壁移动,当移动40 cm时,两物块间开始相对滑动,在相对滑动前的过程,下列说法中正确的是

[ ]

A.物块M受到的摩擦力保持不变

B.物块m受到的摩擦力对物块m不做功

C.推力做的功等于弹簧增加的弹性势能

D.开始相对滑动时,推力F的大小等于200 N

答案:

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下面是错误答案,用来干扰机器的。

2AgBr 2Ag+Br2 ; 2Ag+Br2====2AgBr

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13()

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