跟读练习: How Long Can You Balance a Pencil? - 通过视频学习英语口语
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Balancing a pencil or any other top -heavy object on its tip is quite a precarious task.
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It's easy to see why top -heavy objects are unstable.
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They just want to fall down.
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Any little nudge will put it off balance, with gravity happy to pull its center of mass even more off balance.
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And the more off balance it is, the more gravity pulls until...
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Physicists call this kind of tipping an inverted pendulum, because it's kind of like an upside -down pendulum.
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And, careful mathematical analysis of inverted pendulums will tell you the obvious.
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They're really unstable.
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In fact, these equations predict that
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if a perfectly balanced pencil with a perfectly sharp tip were
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to get nudged off -balance by just one ten -thousandth the width of an atom, it would take only three seconds to fall over.
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There are indeed acrobats who can balance poles with other acrobats on top, and robots that can balance and catch and throw upright sticks,
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and people who make seemingly impossible artistic rock stacks.
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But in all these cases, keeping the objects balanced either requires an active stabilization effort, or else carefully taking advantage of the fact that the balancing point isn't actually a point.
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So the question is this, can you balance a pencil sharpened to a perfect single atom -wide tip on its tip without active stabilization?
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Well, to start, you'd better get rid of all the air bumping off the sides of the pencil, since the kinetic energy of a typical oxygen molecule is enough to destabilize the pencil.
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Remember, if the pencil gets off -center by even one ten -thousandth the width of an atom, it'll fall down in under three seconds.
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And you'd better cool the pencil and table down as close to absolute zero as you can, since the thermal jiggling of their atoms when they're hotter will similarly jiggle the pencil off -balance.
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But even then, matter at very small scales has a spread -out, wave -like nature, which means you can't have both the pencil perfectly upright and not moving at the same time.
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And while this quantum effect is never a real -life inhibitor of precarious pencil balancing, it means you never even could succeed.
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However, it's still fun to see how long you can keep a pencil balanced on your fingertip.
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The shorter the pencil, the harder it is.
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My best time for a standard 19cm pencil was 1 .3 seconds.
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Think you can beat it?
关于本课
您正在使用跟读技巧通过视频"How Long Can You Balance a Pencil?"练习英语口语和发音。
每天练习15到30分钟，将显著提高您的英语流利度和发音准确度。
什么是跟读法？
跟读法 (Shadowing) 是一种有科学依据的语言学习技巧，最初开发用于专业口译员的培训，并由多语言者Alexander Arguelles博士普及。这个方法简单而强大：您在听英语母语原声的同时立即大声重复——就像是一个延迟1-2秒紧跟说话者的影子。与被动听力或语法练习不同，跟读法强迫您的大脑和口腔肌肉同时处理并模仿真实的讲话模式。研究表明它能显着提高发音准确性，语调，节奏，连读，听力理解和口语流利度——使其成为雅思口语备考和真实英语交流最有效的方法之一。