题干

如图所示,物体与一根水平轻弹簧的一端相连,放在水平面上,弹簧的另一端固定在P点,已知物体的质量为m = 2.0kg,它与水平面间的动摩擦因数是0.4,弹簧的劲度系数k =" 200N" / m。用力F拉物体,使它从弹簧处于自然状态的O点向左移动10cm,这时弹簧具有弹性势能是1J,物体处于静止。(g取10m / s2)撤去外力后,物体开始向右滑行    (       )

A:物体向右滑动的距离可以达到12.5cm

B:物体向右滑动的距离一定小于12.5cm

C:物体回到O点时,物体的动能最大

D:物体到达最右位置时,物体的动能为零,弹性势能也为零

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答案(点此获取答案解析)

B

同类题2

阅读下面短文,然后从各题所给的四个选项中选出一个最佳选项。

    My mother only had one eye. And because of this, I never wished her to show up in my  1  , being afraid that my classmates would find out I had an ugly mother.

One day during elementary school, I was terribly ill. My mother came.     "Your mom only has one eye?!" asked some of my classmates. I was so  2 .     I wished my mother would just disappear from this world. "If you make me teased(嘲笑),why don't you just die?" I shouted at her, taking no notice of the sad look on her face. My mother just handed me some  3and left without saying    4   .     At that time, I felt  5  to say what I always wanted to say, and I didn't think I had hurt her feelings very much. That night I saw my mom      6  in her room, so quietly, as if she was afraid that she might   7  me. Even so, I hated her tears from one eye. I made a   8  : I must study hard and leave my mother.     Years later my dream came true. I was quite successful and lived  9 . I never thought of going back to see my "ugly" mother  10 one day I got a letter, which said, "My son... I'm sorry I only have one eye. When you were little, you got into a(n)  11   and lost your eye. As a mom, I couldn't   12  watching you live with only one eye.  13   I gave you mine. I was never  14   with you and I never regretted(后悔) what I did because I    15   you…"     I cried out aloud. Only then did I realize how beautiful my mother was!