题干

图是某课外科技小组的同学设计的厕所自动冲水装置的示意图,它在自来水管持续供给的较小量的水储备到一定量后,自动开启放水阀门,冲洗厕所.实心圆柱体浮体A的质量为5.6kg,高为0.18m,阀门B的面积为7.5×103m2;连接A、B的是体积和质量都不计的硬杆,长为0.16m.当浮体A露出水面的高度只有0.02m时,阀门B恰好被打开,水箱中的水通过排水管开始排出.已知水的密度为1×103kg/m3,不计阀门B的质量和厚度.当水箱开始排水时,求:



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同类题3

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莫扎特的力量

    ①今年是莫扎特诞辰250周年,世界各地的人们都在纪念他。而在过去十年中,人们一直在为莫扎特的乐曲对多种疾病的神奇疗效而惊叹。

    ②为什么莫扎特的乐曲成了人们关注的焦点,而不是巴赫、贝多芬或是肖邦呢?美国一位研究癫痫病的神经科医师约翰·休斯认为,莫扎特乐曲的治疗效果与众不同。研究表明,80%的癫痫症患者因为病房内播放莫扎特D大调交响曲,其痉挛的强度减弱,频率降低,而用其他作曲家的乐曲进行类似的实验,却总是瞎子点灯——白费蜡。

    ③约翰·休斯认为,其奥妙在于莫扎特乐曲中旋律重复的独特方式。莫扎特乐曲中的旋律每20-30秒重复一次,这恰好与我们的脑电波及人体其他中枢社经系统的运行有着几乎一致的频率。于是,莫扎特乐曲中的节拍能够对癫痫病人大脑中不规则的电波起到纠正的效果。他接着解释说,癫痫病人在病情发作时是完全昏迷的。可见,莫扎特的乐曲对大脑有直接影响。

    ④莫扎特的乐曲可以提高智障儿童智力的现象,是目前人们关注最多的。研究发现,智障儿童在聆听莫扎特乐曲10分钟后,可以在智力测验中拿到更多的分数。同样,反复并持续听到莫扎特某一段交响曲的老鼠,在一个复杂的容器中找到出口的速度,要比生活在其他环境中的老鼠快得多。

    ⑤此外,莫扎特的乐曲也能够对孤僻症患者起到很好的治疗效果。麦乐佳顿的女儿是个孤僻症患难与共者,医生对她彩了音乐疗法。她接受治疗时使用的耳机是经过改装过的,这种耳机的作用原理是通过震动头部骨骼的方式传导乐曲。莫扎特的乐曲会给患者的听觉以极大的冲击力,这样,借助音乐的力量,改善了患者与别人交流的能力。麦乐佳顿起初对此种疗法有所怀疑,但是现在她的看法完全改变了。

     ⑥巴黎艺术家卡迪艾力正在为一幅作品的创作而烦恼时,突然失去灵感,完全无法使用蓝绿两色。她也接受了音乐治疗,取得了很大疗效,蓝绿两色又一次地回到了她的画板上。后来她说,莫扎特乐曲的效果实在太惊人了。感觉自己要10年才能完成的心理治疗,仅仅在8个月内就完成了。她感叹:“莫扎特就像我的爷爷,在我被噩梦惊醒时,他会第一个过来安抚我。”

同类题4

下面文章中有五处需要添加小标题, 请从以下选项(A、B、C、D、E和F)中选出符合各段意思的小标题, 选项中有一项是多余选项。

A.Try to be a small animal doctor

B.Help to clean our city

C.Try to give the disabled a hand

D.Make  more money

E.Visit the old people's home

F.Raise money for poor students

     There are usually some people around us who need help. So it's great to be volunteers. But what can we do? Here are some great ideas.

____

    Not every child can go to school in our country. That's because most of them are too poor to pay for their education. But if we try to raise enough money for these students, they'll be able to finish their schools and have better futures.

____

      The city is our home. However, we pollute it every day. It's time to make it cleaner and greener. We should try to pick up rubbish whenever we see it. We can even go to clean up the city streets, the city parks or the rivers near our city when we are free.

____

      They usually have many problems with their everyday life. An easy thing for a common person may be very difficult for them. Reach out your hands to help to carry their bags, take them to cross the roads. Only a little help can make them feel warm

____

      Many of them have no sons or daughters, so they need someone to spend time with. On weekends or some special days, go to see them. It's a good idea to sing or dance for them. Or just tell them small stories to make them feel less lonely.

____

      They are our friends, but some of them are in danger. We should try to protect and save them. If you are lucky to be their doctor, you'll learn more about how to care for them. And when you see them get better, you'll feel happy and proud.