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如图所示,质量M=0.040kg的靶盒A静止在光滑水平导轨上的O点,水平轻质弹簧一端栓在固定挡板P上,另一端与靶盒A连接.Q处有一固定的发射器B,它可以瞄准靶盒发射一颗水平速度为v0=50m/s,质量m=0.010kg的弹丸,当弹丸打入靶盒A后,便留在盒内,碰撞时间极短.不计空气阻力.求:

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同类题4

阅读下文,完成小题。

只想让您听听我的心跳

   这些年来,一直有一个影子在我脑海里,既模糊又特别清晰。在大学毕业之际,我要去揭开这个谜底,完成这个埋藏了十年的心愿。

    19号,我选了这个时间启程,因为19号是一个特别的日子,一个我最喜欢最期待的日子。

   火车驶向春城的黄花小镇,窗外不时闪过的景象,陌生而又熟悉。我小心地抱着书包,紧贴在胸口,那里面,装着我十年的秘密。我仿佛感觉到自己的心跳,是期盼?是激动?或者,两者都有吧。

   下午3点,火车终于到达了我在地图上千百次查看过的黄花小站。当踏上这片土地的时候,我感觉到心跳竟是如此的强烈!有些印象,毫无由来,却异常清晰。

   我在小镇一个僻静的角落里找到了“黄花邮局”。此时的心,竟然那样宁静。我静静地走过去,推开那扇玻璃门。这个样子,原来就是这个样子!站在大厅,我有点手足无措。保安走过来,问我需要什么帮助,我不知所以地点点头,也不知怎么的便坐在了靠门口的座位,因为我要等一个很重要的人。

   3点半,3点40,3点45……我不断地看时间,终于,到了北京时间4点整,大厅的时钟滴答滴答,整点报时。我的心紧张起来。我不由自主地站起来,盯着门口,盯着进来的每一个人。一对老夫妇,脊背佝偻,步履蹒跚,彼此搀扶,径直往窗口走去。

   “还是照以前一样,把钱寄到这个地址。”老人说。旁边的老妇人一定是他的妻子,紧紧靠着他,也使劲地在点头。服务员点点头,迅速地敲打键盘,看得出,她一定为这对夫妇重复过很多次这项工作。我悄悄走过去,清楚地看见,那上面的名字正如自己所料。是他俩,就是他俩!十年累积的情感再也无处藏匿,我的心几乎要跳出来,我好不容易忍住眼泪,终于说出准备了千万次的话语:“父亲,母亲,我就是您10年来一直资助的那个孤儿。”

   10年前,因为一次车祸,我必须做心脏移植手术,而与此同时,在春城,有一个女孩也遭遇了一场车祸,可惜,她没有我幸运,永远地离开了这个世界。但我后来才知道,其实她并没有离去,因为她的父母同意把她的心脏移植到我身上。不仅如此,得知我的父母在车祸中罹难,10年来,他们每个月都会寄一笔生活费给我。

    从邮局查询得知,就是在这里,日期是19号,时间是下午4点。当我终于走向独立,大学毕业,被一家大型企业录用的时候,我要完成感恩的心愿。我终于来到了这里,看到了魂牵梦绕的一切。

   我小心地从书包里取出两串项链,每串项链都用60颗纸折的小红星串成。120个红星,代表着3650个感恩的日子,代表着3650个思念的心情……

   我把项链恭敬地挂在两位老人的胸前。项链渐渐变成了两颗闪闪发光的红心,我分明看到红色的光辉照亮了周围的一切,我分明听到我的心和这两颗红心一齐跳动,我分明感觉到老人的爱已将我包围

   老人紧紧地把我搂在怀里,说:“我的孩子啊,你怎么来啦!”我泪如泉涌,泣不成声。

   父亲,母亲,我过来,只想让您听听我的心跳……

(选自《读者》2013年第11期,有改动)

同类题5

   A 10-year-old boy decided to learn judo though he had lost his left arm in a car accident. The boy was doing well, so he couldn't understand why, after three months of training, the master had taught him only one move.
   “ Master,” the boy finally asked, “shouldn't I be learning more moves?"“ This is the only move you know, but this is the only move you'll ever need to know,” the teacher answered.
   Several months later, the teacher took the boy to his first competition. Surprising himself, the boy easily won his first two matches. The third match proved to be more difficult, but after some time, his opponent (对手) became impatient and charged; the boy skillfully used his one move to win the match. Still amazed by his success, the boy was now in the final.
  This time, his opponent was bigger, stronger, and more experienced. Soon after the match started, the boy seemed to lose. Thinking that the boy might get hurt, the judge called a time-out. He was going to stop the match when the teacher appeared. “ No,” the teacher said, “Let him continue.” A short time after the match carried on, his opponent made a careless mistake. At once, the boy used his move to pin (压住) him. The boy won the match and the competition.
  On the way home, the boy asked the teacher what was really in his mind. " Why could I win the competition with only one move?" The teacher answered. "First, you've mastered one of the most difficult throws in judo. Second, your opponent can only attack your left arm to win you.”
根据短文内容完成下面的表格,每空一词。

Title: One’s weakness can become his____ 
A boy had lost left arm, ____  he decided to learn judo
After three months of training, the master taught him only one move.
His first____ First three matchesHe won.
FinalHis opponent was bigger, ____  and more ____ .
At the ____ , the boy seemed to lose the match.
The judge was____  that the boy might get hurt and called a time-out.
His opponent made a mistake. The boy used his move and pinned him.
He became the ____  of the match.
____ 1. He had almost mastered one of the most difficult throws in all of judo.
 The opponent can win the match by ____  your left arm.