煎蛋小学堂:英语百科(视频+中英字幕) 第18课:用手指尖平衡铅笔的最佳方法
<p><span word="Balancing">Balancing</span> <span word="a">a</span> <span word="pencil">pencil</span> <span word="or">or</span> <span word="any">any</span> <span word="other">other</span> <span word="top">top</span>-<span word="heavy">heavy</span> <span word="object">object</span> <span word="on">on</span> <span word="its">its</span> <span word="tip">tip</span> <span word="is">is</span> <span word="quite">quite</span> <span word="a">a</span> <span word="precarious">precarious</span> <span word="task">task</span>.<span word="Its">Its</span> <span word="easy">easy</span> <span word="to">to</span> <span word="see">see</span> <span word="why">why</span> <span word="top">top</span>-<span word="heavy">heavy</span> <span word="objects">objects</span> <span word="are">are</span> <span word="unstable">unstable</span>.<span word="They">They</span> <span word="just">just</span> <span word="want">want</span> <span word="to">to</span> <span word="fall">fall</span> <span word="down">down</span>.<span word="Any">Any</span> <span word="little">little</span> <span word="nudge">nudge</span> <span word="will">will</span> <span word="put">put</span> <span word="it">it</span> <span word="off">off</span> <span word="balance">balance</span>.<span word="With">With</span> <span word="gravity">gravity</span> <span word="happy">happy</span> <span word="to">to</span> <span word="pull">pull</span> <span word="its">its</span> <span word="center">center</span> <span word="of">of</span> <span word="mass">mass</span> <span word="even">even</span> <span word="more">more</span> <span word="off">off</span> <span word="balance">balance</span>.<span word="And">And</span> <span word="the">the</span> <span word="more">more</span> <span word="off">off</span>-<span word="balanced">balanced</span> <span word="it">it</span> <span word="is">is</span>.<span word="the">the</span> <span word="more">more</span> <span word="gravity">gravity</span> <span word="pulls">pulls</span> <span word="until">until</span>...将铅笔或任何头重的物体平衡在尖端都是在拼人品。显然，头重的物体很不稳定，它们就喜欢趴体。极小的推力就会使其失衡。而重力很乐意使其质心更偏离平衡点，越偏离平衡，重力作用越明显 直到...<span word="Physicists">Physicists</span> <span word="call">call</span> <span word="this">this</span> <span word="kind">kind</span> <span word="of">of</span> <span word="tipping">tipping</span> <span word="an">an</span> <span word="inverted">inverted</span> <span word="pendulum">pendulum</span>,<span word="because">because</span> <span word="its">its</span> <span word="kind">kind</span> <span word="like">like</span> <span word="an">an</span> <span word="upside">upside</span> <span word="down">down</span> <span word="pendulum">pendulum</span>,<span word="And">And</span> <span word="careful">careful</span> <span word="mathematical">mathematical</span> <span word="analysis">analysis</span> <span word="of">of</span> <span word="inverted">inverted</span> <span word="pendulums">pendulums</span> <span word="will">will</span> <span word="tell">tell</span> <span word="you">you</span> <span word="the">the</span> <span word="obvious">obvious</span>:<span word="they">they</span> <span word="are">are</span> <span word="really">really</span> <span word="unstable">unstable</span>.物理学家将这种尖端称为“倒摆”，因为它很像是颠倒的摆锤。对倒摆精确数学分析的结果也显而易见，它们非常不稳定.<span word="In">In</span> <span word="fact">fact</span>,<span word="these">these</span> <span word="equations">equations</span> <span word="predict">predict</span> <span word="that">that</span> <span word="if">if</span> <span word="a">a</span> <span word="perfectly">perfectly</span> <span word="balanced">balanced</span> <span word="pencil">pencil</span> <span word="with">with</span> <span word="a">a</span> <span word="perfectly">perfectly</span> <span word="sharp">sharp</span> <span word="tip">tip</span> <span word="were">were</span> <span word="to">to</span> <span word="get">get</span> <span word="nudged">nudged</span> <span word="off">off</span> <span word="balance">balance</span> <span word="by">by</span> <span word="just">just</span> 1/10,000 <span word="of">of</span> <span word="the">the</span> <span word="width">width</span> <span word="of">of</span> <span word="an">an</span> <span word="atom">atom</span>,<span word="it">it</span> <span word="would">would</span> <span word="take">take</span> <span word="only">only</span> 3 <span word="seconds">seconds</span> <span word="to">to</span> <span word="fall">fall</span> <span word="over">over</span>.<span word="There">There</span> <span word="are">are</span> <span word="indeed">indeed</span> <span word="acrobats">acrobats</span> <span word="who">who</span> <span word="can">can</span> <span word="balance">balance</span> <span word="poles">poles</span> <span word="with">with</span> <span word="other">other</span> <span word="acrobats">acrobats</span> <span word="on">on</span> <span word="top">top</span>.<span word="and">and</span> <span word="robots">robots</span> <span word="that">that</span> <span word="can">can</span> <span word="balance">balance</span> <span word="and">and</span>,<span word="catch">catch</span> <span word="and">and</span> <span word="throw">throw</span> <span word="upright">upright</span> <span word="sticks">sticks</span> <span word="and">and</span> <span word="people">people</span> <span word="who">who</span> <span word="make">make</span> <span word="seemingly">seemingly</span> <span word="impossible">impossible</span> <span word="artistic">artistic</span> <span word="rock">rock</span> <span word="stacks">stacks</span>,<span word="But">But</span> <span word="in">in</span> <span word="all">all</span> <span word="these">these</span> <span word="cases">cases</span>,<span word="keeping">keeping</span> <span word="the">the</span> <span word="objects">objects</span> <span word="balanced">balanced</span> <span word="either">either</span> <span word="requires">requires</span> <span word="an">an</span> <span word="active">active</span> <span word="stabilization">stabilization</span> <span word="effort">effort</span>,<span word="or">or</span> <span word="else">else</span> <span word="carefully">carefully</span> <span word="taking">taking</span> <span word="advantage">advantage</span> <span word="of">of</span> <span word="the">the</span> <span word="fact">fact</span> <span word="that">that</span> <span word="the">the</span> <span word="balancing">balancing</span> <span word="point">point</span> <span word="isnt">isnt</span> <span word="actually">actually</span> <span word="a">a</span> <span word="point">point</span>.实际上，这些等式说明，如果一个尖端极其锐利 处于完美平衡的铅笔受到推力失衡，偏离原子长度的万分之一，倒下只需不到三秒。的确有杂技演员可以平衡顶端站人的杆子，有机器人可以平衡 抛掷或接住竖直棒，有人可以堆出看似不可能的石堆。但这些情况中，保持物体平衡，要么需要动态平衡支持，要么谨慎地利用算不上点的“平衡点”。<span word="So">So</span> <span word="the">the</span> <span word="question">question</span> <span word="is">is</span> <span word="this">this</span>:<span word="Can">Can</span> <span word="you">you</span> <span word="balance">balance</span> <span word="a">a</span> <span word="pencil">pencil</span> <span word="sharpened">sharpened</span> <span word="to">to</span> <span word="a">a</span> <span word="perfect">perfect</span> <span word="single">single</span> <span word="atom">atom</span> <span word="wide">wide</span> <span word="tip">tip</span> <span word="on">on</span> <span word="its">its</span> <span word="tip">tip</span>,<span word="without">without</span> <span word="active">active</span> <span word="stabilization">stabilization</span>?<span word="Well">Well</span> <span word="to">to</span> <span word="start">start</span>,<span word="youd">youd</span> <span word="better">better</span> <span word="get">get</span> <span word="rid">rid</span> <span word="of">of</span> <span word="all">all</span> <span word="the">the</span> <span word="air">air</span> <span word="bumping">bumping</span> <span word="on">on</span> <span word="the">the</span> <span word="sides">sides</span> <span word="of">of</span> <span word="the">the</span> <span word="pencil">pencil</span>.<span word="since">since</span> <span word="the">the</span> <span word="kinetic">kinetic</span> <span word="energy">energy</span> <span word="of">of</span> <span word="a">a</span> <span word="typical">typical</span> <span word="oxygen">oxygen</span> <span word="molecule">molecule</span> <span word="is">is</span> <span word="enough">enough</span> <span word="to">to</span> <span word="destabilize">destabilize</span> <span word="the">the</span> <span word="pencil">pencil</span>.那么，问题在此，你能否将一只铅笔平衡在其原子大小的尖端，而不需要动态平衡吗？一开始 你最好排空碰撞着铅笔各面的空气。因为单是氧原子的动能就足以让铅笔失衡。<span word="Remember">Remember</span>,<span word="if">if</span> <span word="the">the</span> <span word="pencil">pencil</span> <span word="gets">gets</span> <span word="off">off</span> <span word="center">center</span> <span word="by">by</span> <span word="even">even</span> 1/10,000 <span word="the">the</span> <span word="width">width</span> <span word="of">of</span> <span word="an">an</span> <span word="atom">atom</span>,<span word="it">it</span> <span word="will">will</span> <span word="fall">fall</span> <span word="down">down</span> <span word="in">in</span> <span word="under">under</span> 3 <span word="seconds">seconds</span>.<span word="And">And</span> <span word="youd">youd</span> <span word="better">better</span> <span word="cool">cool</span> <span word="the">the</span> <span word="pencil">pencil</span> <span word="and">and</span> <span word="table">table</span> <span word="down">down</span> <span word="as">as</span> <span word="close">close</span> <span word="to">to</span> <span word="absolute">absolute</span> <span word="zero">zero</span> <span word="as">as</span> <span word="you">you</span> <span word="can">can</span>,<span word="since">since</span> <span word="the">the</span> <span word="thermal">thermal</span> <span word="jiggling">jiggling</span> <span word="of">of</span> <span word="their">their</span> <span word="atoms">atoms</span> <span word="when">when</span> <span word="they">they</span> <span word="are">are</span> <span word="hotter">hotter</span> <span word="will">will</span> <span word="similarly">similarly</span> <span word="jiggle">jiggle</span> <span word="the">the</span> <span word="pencil">pencil</span> <span word="off">off</span> <span word="balance">balance</span>.记住，如果铅笔偏离平衡点万分之一原子的距离，它就会在3秒内倒下，你也最好将铅笔和桌子尽可能地冷却到绝对零度。因为原子温度较高时的热振动，也会将铅笔“振”倒。<span word="But">But</span> <span word="even">even</span> <span word="then">then</span>,<span word="matter">matter</span> <span word="at">at</span> <span word="very">very</span> <span word="small">small</span> <span word="scales">scales</span> <span word="has">has</span> <span word="a">a</span> <span word="spread">spread</span> <span word="out">out</span> <span word="wave">wave</span>-<span word="like">like</span> <span word="nature">nature</span>,<span word="which">which</span> <span word="means">means</span> <span word="you">you</span> <span word="cant">cant</span> <span word="have">have</span> <span word="both">both</span> <span word="the">the</span> <span word="pencil">pencil</span> <span word="perfectly">perfectly</span> <span word="upright">upright</span> <span word="and">and</span> <span word="not">not</span> <span word="moving">moving</span> <span word="at">at</span> <span word="the">the</span> <span word="same">same</span> <span word="time">time</span>.<span word="And">And</span> <span word="while">while</span> <span word="this">this</span> <span word="quantum">quantum</span> <span word="effect">effect</span> <span word="is">is</span> <span word="never">never</span> <span word="a">a</span> <span word="real">real</span> <span word="life">life</span> <span word="inhibitor">inhibitor</span> <span word="of">of</span> <span word="precarious">precarious</span> <span word="pencil">pencil</span> <span word="balancing">balancing</span>,<span word="it">it</span> <span word="means">means</span> <span word="you">you</span> <span word="never">never</span> <span word="even">even</span> <span word="could">could</span> <span word="succeed">succeed</span>.即使这样，十分微小的物质具有类似于波的本质，也就是说，铅笔完全竖直与保持平衡不动，不可同时兼得。尽管量子效应不会对你拼人品平衡铅笔带来真实影响。者却意味着 你永远做不到。<span word="However">However</span>,<span word="its">its</span> <span word="still">still</span> <span word="fun">fun</span> <span word="to">to</span> <span word="see">see</span> <span word="how">how</span> <span word="long">long</span> <span word="you">you</span> <span word="can">can</span> <span word="keep">keep</span> <span word="a">a</span> <span word="pencil">pencil</span> <span word="balanced">balanced</span> <span word="on">on</span> <span word="a">a</span> <span word="finger">finger</span> <span word="tip">tip</span>.<span word="The">The</span> <span word="shorter">shorter</span> <span word="the">the</span> <span word="pencil">pencil</span>,<span word="the">the</span> <span word="harder">harder</span> <span word="it">it</span> <span word="is">is</span>,<span word="My">My</span> <span word="best">best</span> <span word="time">time</span> <span word="for">for</span> <span word="a">a</span> <span word="standard">standard</span> 19<span word="cm">cm</span> <span word="pencil">pencil</span> <span word="was">was</span> 1.3<span word="s">s</span>.<span word="Think">Think</span> <span word="you">you</span> <span word="can">can</span> <span word="beat">beat</span> <span word="it">it</span>?不过，看看你能用指尖平衡铅笔多长时间也很有意思。铅笔越短 难度越大。我的标准19厘米铅笔最好记录是1.3秒。你行你上啊？</p>
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