一个方法: 把至少一半的金属片叠在一起伸出桌面1/4 (设金属片长度为1) 再把剩下的至少一半叠在一起放在前面一堆的上面伸出桌面(1/4+1/5) 如此类推,因为 (1/4+1/5+1/6+。。。) 是发散级数,和可以任意大,只要有足够多的金属片。
因为每一堆的重心都在下面一堆的面内,如果加上新一堆后,下面一堆不掉下来,上面一堆也不会掉下来,所以要掉是整个一起掉。这样只要算总的重心,是否在桌面内。不知道这样说力学上对不对?
证明:不妨假设有2n 张金属片,桌子边为0点,桌子在右边,那么如果重心是正的,就不会掉下来: 第1堆 2(n-1) 张,重心坐标是1/4 第2堆 2(n-2) 张,重心坐标是1/4-1/5 第3堆 2(n-3) 张,重心坐标是1/4-1/5-1/6 ... 第n堆 20=1 张,重心坐标是1/4-1/5-1/6-....-1/(n+3)
所有这 2n-1张,重心坐标为: X=1/4-1/5*[1+2+4+....+2(n-2)] / [2n-1] -1/6*[1+2+4+....+2(n-3)] / [2n-1]- .... 而 [1+2+4+....+2(n-2)] / [2n-1] = [2(n-1)-1] / [2n-1] < 1/2 [1+2+4+ .... +2(n-3)] / [2n-1]=[2(n-2) -1] / [2n-1] < 1/4 。。。 X>1/4-1/5*1/2-1/6*1/4-....>1/4-1/5*(1/2+1/4+1/8+....) >1/4-1/5>0
其实每一堆比下面一堆都多伸出1/5就可以了 ,证明相同.
|
Thank you for your support At the same time, hope the Chirstian forum is getting better and better |
Christian forum needs your help more! |
Sorry, 没注意这个条件:每一片都比前一片多伸出桌面一点。 那就每一片比原来的堆法多伸出可以忽略不计的一点点,比如( 1/2n) n, 应该对证明没有什么影响。 |
1/4+1/5+.......+1/n是无穷大吗? 本来就是不可能的。
|
1/4+1/5+.......是无穷大 所以只要 n 足够大,1/4+1/5+.......1/n 也可以任意大 |
绝不可能无限叠加 |
这道题可以有无数种方法,关键点是为了使伸出桌面部分越长,放在下面的应该足够重(张数足够多)。 |
What a stupid moron! Think hard beofre you believe you are smarter than others. |
Seriously, he is not that ignorant -- he made it very clear that he knows that: the whole stack will fall if the center of gravity is off the edge of the table -- quite some achievement, don't you agree? I'm pretty sure, within the next several years, and with some serious effort, he will manage to understand some of the solutions posted here, and hopefully will learn a math lesson as well as a moral one. Give him some time, would you? |
都是我的错,我忽略了一点:它其实根本就看不懂那些解法的。更大的错误在于,这种到脑坛这种藏龙卧虎的地方上来就数学,物理的多半精神有点问题。可叹我还回了它两贴。 |
我的总结陈词 -- 总结 is obviously not necessary, since you haven't make any valuable points, and 陈词? come on, no one takes you that serious, except, of cause, yourslef. 1)不要以为别人都是白痴。... Interesting to hear YOU say so. (2)任何问题的解答,首先要弄清问题本身:是物理问题或者现象呢,就要认真去研究解答,免不了用到数学推证。是纯数学问题比如 四色猜想、哥德巴赫猜想等等,就是纯数学的解答。但千万不能将一个不可能发生的物理现象假设发生了,然后去用数学推论出来。这种假设的问题加上严格的数学推论,得出的结论依然是个不可能发生的现象。 ----本问题的实质就是假设一个现象发生了,然后去推证。其实这个现象不存在。 。。 You have make up your mind that the problem is impossible, and just regard that as the truth. If you really want to think about it, first read others' post more carefully, as I said, I'm confident that you will understand those solutions -- perhaps with some serious efforts, don't give up, you can do it! (3)结论:数学在其它领域永远只是“认知的工具”而决不是改变自然科学内部规律的法宝。 。。 A seemingly deep word, such as “认知的工具”, combined with the funny "陈词" you made, only shows how shallow you are. 祝朋友们快乐! Happy thinking time! |
If you think 丘XX目空一切, well, at least he has that 'capital'. What do you have to call others 白痴? You are just a joke, why don't you just do yourself a favor and jsut shut up? |
看看你发的第一个挑衅贴,那才是标准的粪青。本着治病救人的目的再问你两个问题:你能不能再好好想一想为什么物理上不可能?难不成你就是传说中的耶稣,你说了算?是男人的话好好想清楚了上来跟大家道个谦!更男人的话,应该谢谢xlxk和BePatient对你的诲人不倦! |
说到耶苏这位鲁迅迅网友的感触应该比任何人都来得深,哈哈哈。。。 我同情这位网友,除了骂人和扭曲事实,什么都不会,就像受了刺激的怨妇。 别带着怨气上网,为了你的健康。 |
精神有点失常了吧,"忍不住说几句"说你呢! |
个人觉得你肯定喜欢手淫-不能过正常性生活的变态萎缩男! |
我不得不承认这是一个不可教化的傻比!大家都剩下精力干别的去吧! |
xlxk,骂人可不对,尽管我可以理解你的心情。鲁迅迅你也太无知无畏了,跟我上初一的外甥似的! |
恩,气糊涂了,本着好心想教化它一下、、、不过说到骂人,去看看它的第一个贴:一上来就骂大家都是呆子,白痴,尽管从回帖来看,事实正好相反。 |
有时候不能太纵容鲁迅迅这种网友,虽然我也不提倡骂人,但是对待某些人就应该用这种方式。骂了才会清醒,他应该感谢xlxk对他的教诲! |
总结一下:(1)题目是误导人的。其实根本不可能最后一片完全伸出桌面。什么论点,其实是一个根本不可能的事情,还有人跟贴说小时候玩过什么砖块什么竞赛。哈哈。。。人啊。。 Do the following experiment: Get a deck of playing cards. Put 50 of the cards at the edge of a table, so that the gravity center is close to the edge. Put the remaining 4 cards one by one on the top, each placed outward by some (approximately) fixed amount. With several adjustment, you will get the case where the last card is outside the table. If you must, you can adjust your base deck (the 50 cards) slightly outwards, so that all conditions of the problem is strictly met. In case you don't have cards handy, here is a picture, hope you are convinced. http://upload.ddhw.com/show.aspx?id=48427.jpg |
good example. 真奇怪那逼人成天物理,数学的,就不知道自己动手试一试?真他妈的一极品!! |
看看你的丑陋表演: 哈哈哈哈哈哈哈哈哈哈哈哈。。。。。。。。。。。。噢勒噢勒噢勒噢,无限延伸了。。。。最后的扑克牌完全伸出桌面了。。。上帝给支撑着呢,怕什么。。。。数学公式给支撑呢,怕什么。数学证明给支撑着呢。。。哈哈哈哈哈哈。。。。 你以前一直声称问题的实质是:最上面一块不可能伸出桌面么!! 认个错对你来说那么难么?你不是只看物理?不管数学么?BePatient告诉你物理上最上面一块可以伸出桌面,你去反驳那个贴子去。 我诚恳地建议: 1。象男人一样认个错吧,要不你只能是自寻其辱!! 2。认真看野菜花的帖子,不要信口雌黄。 3。请个家教补习一下数学(给你提供点线索:野菜花对重心的推导是正确的。如果你需要,我可以提供更优雅的数学证明,不过野菜花的帖子你都看不懂的话,我看还是算了)。 |
<别生气了噢> How can any one get angry with you? You are the best comedian this forum ever see. We just try to make yourself realize how humourous you are. <是我顽固不化吗?因为我是学工程搞工程研究的,懂得物理现象必须符合基本的原理,常识有时就是基本的原理。> A "常识" like "最上面一块不可能伸出桌面"? <作者的假设是二分法,就是离散的快速傅里埃变换FFT(Fast Fourier Transform)的假设类似一样即:样本是可以等比二分的,> How does 二分法 has anything to do with this problem? Does anyone try to solve for the root of some function? Is 样本是可以等比二分的 how you understand 二分法? -- Very intuitive name, right? I would suggest you to post this kind of funny usage of math terms in 舞文弄墨, where (my pure guess) many people do not know a lot of math terms by training -- no guarantee though, don't blame me if your Niu(2)Pi(2) is also busted there. |
这个无知的东西想通过一些数学术语来证明他不是那么无知。这个问题跟FFT没有任何关系,可怜他同一术语重复了三遍。什么二分法,等比二分看了也是让人不知所云!至于他肆意歪曲野菜花的帖子,更是让人无语! |
<我是死猪不怕开水烫的了.> I like your honest self evaluation. |
<其实我按照野菜花的假设推导了一遍,结论是X>0。可是,就喜欢看你生气的德行。。。> So, you agree you have been wrong, and those what you called 数学呆子,物理白痴 have been right? Is this way of admitting mistake too subtle compare to the way you called other 呆子 and 白痴? <我其实懒得回贴的...> Please, don't get discouraged by those negative comments on your great posts. I love to hear more about your great comments on 问题的实质, on 二分法, on 重心问题, and expecially on your great 常识 (==基本的原理) -- without these humorous comments, this forum is just too boring. Although I have suggested you to shut up for your own good, I know you are so unselfish, that you will sacrifice yourself for the amusment of others. |
拜托,要么中文要么英文。 You will get used to my poor English, just like I am getting use to your funny usage of all those terminologies. 祝你愉快噢! Thank you. With a great comedian like you around, I'm pretty sure I will be well entertained here. |
也不觉得自己可怜,我看你是够贱的跑这儿找挨骂 贱人看的多了,像你这么这么这么贱的还是头一回遇见,哈哈哈哈哈.......笑翻了...... 贱人,继续你的表演吧. 哈哈哈哈.....给贱人鼓掌.....哈哈哈哈哈哈 |
原来这个傻逼还是有可能看懂某些帖子的呀?就是不知道是不是吹牛皮? 回去闻闻你自己拉的那些东西!真奇怪还有脸到这儿来! |
把你这些垃圾解释给你父亲听听,看看他会不会后悔当初没把你射墙上! |
The guy need help to understand his ignorance, but he didn't use dirty words (as far as I know), so, let's not go too far. |
欢迎光临 珍珠湾ART (http://zzwav.com/) | Powered by Discuz! X3 |