题干

弹簧振子做简谐运动时,从振子经过某一位置A开始计时,则(      )

A:当振子再次与零时刻的速度相同时,经过的时间一定是半个周期

B:当振子的加速度再次与零时刻的加速度相同时,一定又到达位置A

C:当振子再次经过A时,经过的时间一定是半个周期

D:一定还有另一个位置跟位置A有相同的位移

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答案(点此获取答案解析)

B

同类题2

根据短文内容,选择最佳答案。

    When high school started, Sally and I became best friends. We shared many interests and quickly became very close.When high school ended, we both cried because we would enter different 1 in autumn.

    Our first term of college life was 2, so we often sent long e-mails and encouraged each other. We missed each other so much! In the second term, I found some new friends and I felt very 3 with them. These were friends with whom I could be myself and pour out my feelings. I wanted to share my new friends with Sally.

    When Sally 4 visited me at my school, we were excited.

    She brought a toy bear to me 5a present and told me about her college life. 6, something unexpected happened when I introduced her to my new friends.Her eyes grew dark and I could see the sadness in them.My new friends tried to share their friendship, but Sally seemed unwilling to accept it.I didn't understand 7the people I loved most couldn't love each other.

    Sally left. I knew she was not happy. I thought long about what had happened. I asked her many questions but she didn't answer me. I 8 that she was jealous(嫉妒). She saw me with my new friends and was afraid that we no longer shared the same experiences. She saw that I could still enjoy myself  9 her and wished she could be a part of it.

    I wrote Sally a letter to 10 she's always my best friend. I told her everyone had friends from home and friends from school, and all the friends were indeed life's greatest 11.Sally wrote me back soon. She was in agreement and felt sorry about 12 she had done.

    I think Sally and I both 13 an important lesson from it. Nothing can influence our 14  and change the experiences we've shared.We are now walking on two different paths of life. While new friends are special and exciting, old friends are 15 there, waiting to share their heart, no matter how far away they are from each other.

同类题5

阅读下面文字,完成后面的问题。 

“你该死!你该死!”他们大声嚷着。

树林一直不停地发出低沉的声音,来响应他们的叫嚷,电光把黑暗撕成了碎片。丹柯望着那些人,那些受够了苦的人,他看见他们现在跟野兽完全一样。许多人把他围住,可是他们的脸上没有一点高贵的表情,他不能够期望从他们那儿得到宽恕。于是怒火在他的心中燃起来,不过又因为怜悯人们的缘故灭了。他爱那些人,而且他以为,他们没有他也许就会灭亡。所以他的心又发出了愿望的火:他愿意搭救他们,把他们领到一条容易走的路上去,于是在他的眼睛里亮起来那种强烈的火的光芒……可是他们看见这个,以为他发了脾气所以眼睛燃烧得这么亮,他们便警戒起来,就像一群狼似的,等着他来攻击他们;他们把他包围得更紧了,为着更容易捉住丹柯,弄死他。可是他已经明白了他们的心思,因此他的心燃烧得更厉害了,因为他们的这种心思使他产生了苦恼。

然而树林一直在唱它那阴郁的歌,雷声隆隆地响,大雨依旧在下着……

“我还能够为这些人做什么呢?”丹柯的叫声比雷声更大。

忽然他用手抓开了自己的胸膛,从那儿拿出他自己的心来,把它高高地举在头上。

他的心燃烧得跟太阳一样亮,而且比太阳更亮,整个树林完全静下去了,林子给这个伟大的人类爱的火炬照得透亮;黑暗躲开它的光芒逃跑了,逃到林子的深处去,就在那儿,黑暗颤抖着跌进沼地的龌龊的大口里去了。人们全吓呆了,好像变成了石头一样。

“我们走吧!”丹柯嚷着,高高地举起他那颗燃烧的心,给人们照亮道路,自己领头向前奔去。

他们像着了魔似的跟着他冲去。这个时候树林又发出了响声,吃惊地摇动着树顶,可是它的喧响让那些奔跑的人的脚步声盖过了。众人勇敢地跑着,而且跑得很快。他们都让燃烧的心的奇异景象吸引住了。现在也有人死亡,不过死的时候没有抱怨,也没有眼泪。可是丹柯一直在前面走,他的心也一直在燃烧,燃烧!

树林忽然在他们前面分开了,分开了,等到他们走过以后,它又合拢起来了,还是又密又静的。丹柯和所有的人都浸在雨水洗干净了的新鲜空气和阳光的海洋里。在那边,在他们的后面,在林子的上空,还有雷雨,可是在这儿,太阳发出了灿烂的光辉,草原一起一伏,好像在呼吸一样,草叶带着一颗一颗钻石一样的雨珠在闪亮,河面上泛着金光……黄昏来了,河上映着落日的霞光,显得鲜红,跟那股从丹柯的撕开的胸膛淌出来的热血是一样的颜色。

骄傲的勇士丹柯望着横在自己面前的广大的草原——他快乐地望着这自由的土地,骄傲地笑起来。随后他倒下来——死了。

充满了希望的快乐的人们并没有注意到他的死,也没有看到丹柯的勇敢的心还在他的尸首旁边燃烧。只有一个仔细的人注意到这个,有点害怕,拿脚踏在那颗骄傲的心上……那颗心裂散开来,成了许多火星,熄了……

在雷雨到来前,出现在草原上的蓝色火星就是这样来的!

——节选自《丹柯》