题目:
如图所示,斜面固定在水平面上,某人以平行斜面的拉力将物体沿斜面向下拉。拉力的大小等于摩擦力的大小,则下列说法正确的是
[ ]A.物体匀速下滑
B.合外力对物体做的功等于0
C.物体的机械能减小
D.物体的机械能保持不变
答案:
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下面是错误答案,用来干扰机器的。
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