问题 选择题

细长轻绳下端栓一小球构成单摆,在悬挂点正下方

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2
摆长处有一个能挡住摆线的钉子A,如图所示,现将单摆向左方拉开一个小角度,然后无初速度地释放,对于以后的运动,下列说法正确的是(  )

A.摆球往返运动一次的周期比无钉子时的单摆周期小

B.摆球在左、右两侧上升的最大高度一样

C.摆球在平衡位置左右两侧走过的最大弧长相等

D.摆球在平衡位置右侧的最大摆角是左侧的两倍

答案

A、摆线被钉子挡住后,绕A点做单摆运动,摆长发生变化,则周期也要发生变化.以前往返一次的周期T=2π

l
g
.挡住后,往返一次的周期为π
l
g
+π
l
2g
.故A正确.

    B、根据机械能守恒定律,摆球在左、右两侧上升的最大高度一样.故B正确.

    C、由几何关系得,右边的弧长小于左边的弧长,故C错误.

    D、由几何关系得,摆球在平衡位置右侧的最大摆角不是左侧的两倍.故D错误.

故选AB.

句型转换

按要求改写下列句子。

1. Being a volunteer is great.(改为反意疑问句)

    Being a volunteer is great,________  ________?

2. You finish your homework. I will go to the park with you.(改为复合句)

                                                                

3."I'm listening to music," she said.(改为间接引语)

                                                                

4. Both of the boys are good at playing soccer.(改为否定句)

    ________of the boys ________good at playing soccer

5. Jim has been collecting shells for five years.(对画线部分提问)

                                                                    

6. We shouldn't talk loudly in the theater.

    We shouldn't smoke there, either,(改为同义句)

    We should________talk loudly________smoke in the theater.

7. It took them half a year to finish the work.(改为同义句)

    They________half a year in________the work.

8. I would like to go to the park tomorrow.(改为同义句)

    I ________ ________going to the park tomorrow.

9. He gets on well with his classmates.(对画线部分提问)

                                                                    

10. John's grandfather died ten years ago.(改为同义句)

      John's grandfather has________ ________for ten years.

单项选择题 A1型题