题干

质量为m,速度为v的A球与质量为3m静止的B球发生正碰,碰撞可能是弹性的,也可能是非弹性的,碰撞后B球的速度可能有不同的值,碰撞后B球的速度大小可能是(   )

A:0.6v

B:0.4v

C:0.2v

D:v

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答案(点此获取答案解析)

B

同类题2

阅读理解

    It was Mother's Day morning last year and I was doing my shopping at our local supermarket with my five-year-old son, Teayson. As we were leaving, we found that only minutes earlier an elderly woman had fallen over at the entrance and had hit her bead on the concrete. Her husband was with her, but there was blood everywhere and the woman was embarrassed and clearly in shock.

    Walking towards the scene, Tenyson became very upset about what had happened to the couple. Ile said to me. “Mums it's not much fun falling over in front of everyone.”

    At the front of the supermarket a charity group had set up a stand selling cooked sausages and flowers to raise funds. Tenyson suggested that we should boy the lady a flower. “It will make her feel better,” he said. I was amazed that he'd come up such a sweet idea. So we went over to the flower seller and asked her if we could buy a flower for the lady to cheer her up. “Just take it,” she replied. “I can't take your money for such a wonderful gesture.”

    By now paramedics(救援人员) had arrived, and were attending the injured woman. As we walked up to her, my son became intimidated by all the blood and medical equipment. He said he was just too scared to go up to her.

    Instead I gave the flower to the woman's husband and told him. “My son was very upset for your wife and wanted to give her this flower to make her feel better.”

    At that, the old man started crying and said, “Thank you so much, you have a wonderful son, Happy Mother's Day to you.”

The man then bent down and gave his wife the flower, telling her who it was from. Though badly hurt and shaken, the old lady looked up at Tenyson with love in her eyes and gave him a little smile.

同类题3

阅读下面的文字,完成后面题。

    浅阅读指一种浅层次的、以简单轻松甚至娱乐性为目的的阅读形式,是流于文本浮表、感受愉悦的过程;而深度阅读以提升学识修养和理论思维、工作能力为目的,是对文本蕴含的思想、知识、智慧、情感及其艺术韵致乃至语言品位进行体悟和摄取的审美进程,是读者与作者心与心之间的深入沟通,是对社会与人生意义的探寻和追问,是激发想象和创造活力的情感活动。

    “深度阅读”,它和浅俗化阅读相对,不仅阅读对象不同,而且使用的终端也不尽相同。阅读本如听歌、看画一样,怎样做是个人的自由。但在拥抱数字媒体,浅俗化阅读、碎片化阅读和快餐式阅读渐趋弥漫的当下,“深度阅读”关系到重大的社会问题,也就是说,深度阅读的提倡,阅读习惯的培育和阅读体验的重建,不仅关乎个人的命运,还直接影响到社会风气、民族前途和国家未来。正如作家贾平凹所说:“现在,人们为了生计,整天忙忙碌碌,读书成了一种奢侈。如果人人都不爱读书,国家的发展就没后劲了。”

    深度阅读通常意味着对书籍、期刊等纸媒的阅读,所包含的内容是几千年来人类文明的菁华——宇宙的奥秘、历史的反复、世界各地文化差异的比较、对生命意义的哲学思考乃至小说诗歌等表现人性的文字……有深度的、优质的文章,虽然读起来吃力,却使大脑处于一种安静的、思维高度集中的活跃状态,不仅可以丰富头脑、增强智慧,还能安宁地和自己相处,与灵魂对话,进行终身学习,为个人的精神成长和人生境界提升提供充分的养料。

    我国古代有“多而不求于心,则为俗学”,“读书不向自家身心做功夫,虽读尽天下书无益也”之说,就是在说,浅俗化的阅读不能滋养身心,经世致用,往往会造成有知识没文化,有文化没教养的状况,同时窒闷想象力和创造力的焕发。“凿壁偷光”、“悬梁刺股”等刻苦读书的优良传统,也警策人们努力抵御各种诱惑,用顽强的意志养成静心阅读的习惯。“读书当读全书,节抄者不可读”,“读书无源委,有如断港流,濡润涔蹄间,不能溉田畴”,是在告诫人们,断章取义、掐头去尾的读书,肢解扭曲的名著讲授,就像把河水截断,用牛蹄窟里装的水灌溉庄稼,怎么能滋润心田呢?

    在严肃作家和学者眼中,数字化阅读危害极大。很多读者渐渐认识到八卦、段子、社会新闻无法填补精神空洞,不能够提升自我,反而无谓地浪费时间和精力,慢慢地趋向于读一些有系统知识、有深度的文章和书籍,比较经典的著作回到了人们的视野中。在今年举办的上海书展上,我们也看到了深度阅读的复苏迹象。由元史专家蔡美彪撰写的《中华史纲》,是一本比较偏学术的著作,不想发行量却达到5万册。

    近年来,国内外众多报纸纷纷转型创办网络版和手机版,而书籍的数字化趋势,也有助于在电子终端上拓展深度、冷静和理性的阅读。一个国家,需要的是有远大理想、有创造激情、有头脑且精神高扬的国民,而不是拾人牙慧、思想浅薄和低级趣味的民众。推进全民阅读,倡导深度阅读的好风气,是当前我们社会建设、国家发展所迫切需要的。