题干

关于单摆的运动,下列说法中正确的是

A:单摆摆动过程中,摆线的拉力和摆球重力的合力为回复力

B:摆球通过平衡位置时,所受合力为零

C:摆球通过平衡位置时,所受回复力为零

D:摆球摆动过程中,经过最大位移处时所受合力为零

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答案(点此获取答案解析)

C

同类题2

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    Texting while walking is something that most of us are guilty of. We can't help replying to that message we just received. However, while it's fun to keep up with the latest gossip, we may actually be putting ourselves in danger.

    A team of researchers from two UK universities recently found that people who use their phones while on the move walk differently than usual.

    “Recently, a person in front of me was walking very slowly and weaving (迂回行进), and I thought, 'Is this person drunk?'” Matthew Timmis, co-author of the study, told the Guardian.

    It turned out that the person was just texting. Inspired by this, Timmis and his team set out to discover the effects of phone use on how we navigate streets.

    A group of 21 volunteers were asked to walk around a simulated (模拟的) street, complete with obstacles such as a step. The participants traveled the course a total of 12 times each, either writing or reading a message, making a call, or with no phone at all.

    It took the volunteers 118 percent longer to complete the course when using a phone. They also focused on the step obstacle 60 percent more and paid attention to the travel path 51 percent more when they weren't using a phone.

    Although there were no accidents, Timmis believes we should still be aware of what's going on around us.

    “The big risk here is suddenly-appearing hazards (危险), like a pedestrian (行人) suddenly walking in front of you,” he told the Guardian. “You are not going to be able to respond to that as efficiently, which increases the risk of injury.”

    To bring attention to the dangers of “text walking”, a temporary “texting lane” was set up in Antwerp, Belgium in 2015. And earlier this year, a special crosswalk featuring flashing red lights on the ground to get the attention of texters was set up in Wuhan, Hubei province.

    “Texting while walking can lead to collisions with poles or other pedestrians. You could even be endangering your own life when you cross the street without looking up,” a spokesperson for the company that made the Antwerp texting lane told Yahoo News.

同类题5

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    [甲]中国的字画艺术源远流长。历朝历代,书法家、画家,名家辈出,名作如林,如同星月交辉,共同创造了灿烂的东方文明。只要你涉足中国字画的领域,你就会被中国字画独特的魅力所吸引,被中国字画的博大精深所感染。世界艺术大师毕加索看了张大千的画后,慨然说道:“艺术在你们中国。”连“野兽派”画家的代表人物马蒂斯都承认:“我的灵魂长来自东方的艺术。”客观地说,真正能把握中国字画神韵的还是中国人自己。历代那些或幼稚或淡雅或灿烂的绘画名品,本质上是书画艺术家们以自己独特的审美方式与主客体世界进行心灵对话的形象记录。这种对话有时达到了哲学化的高度——在“若坐、若行、若飞、若动”的纵横笔画之间,在“微茫惨淡”“有风致、有缥缈”的笔情墨像之间,蕴含着情思,体现着“道”,表现着对人格乃至对宇宙、生命的体验。中国字画在某种意义上标志着华夏文明在古典文化艺术领域的最高水准,是中华民族的聪慧与创造力最集中的一种表现。

    [乙]我爱好音乐。我经常被那宁静如水、孔明如前的乐声所陶醉。这次深山听泉,我又产生了与聆听乐曲相同的感受。

    深夜听泉,另有一番滋味。全声浸着月光,听来格外清晰。白日里浑然一片的泉鸣,此时却能分出许多层次:那柔曼如听琴者,是草丛中淌过的小溪;那清脆如弹拨者,是石缝间漏下的滴泉;那厚重如倍司轰响者,应为万道细流汇于深潭。清流拍打着卵石则轻重缓急,远近高低,各自发出互不相同的音响。这万般泉声,汇成一曲美妙的交响乐,在这泉水的交响之中,仿佛能够听到岁月的流逝、历史的变迁、生命的繁衍……我俯身倾听着,分辨着,我的心犹如溶于水中随泉而流,随乐起伏。又好像泉水汩汩滤过心田,冲走污垢,留下纯洁,任我品味,引我遐想。啊,我完全陶醉在泉水的歌唱之中。泉水就是大山的灵魂。我感觉用泉水荡涤过的心田,如同用音乐耕耘过一样,能开出清新、典雅的花朵。