跟读练习: How Tire Rolling Resistance Affects Cycling Speed ? - 通过视频学习英语口语
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What is rolling resistance and why should you think about it on the bike?
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Rolling resistance is, quite simply, the energy that is lost as a tyre rolls along a surface.
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The energy is mostly lost because of the constant deformation of that tyre against the surface.
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Now, whilst paying attention to rolling resistance is important, it's not actually the biggest resistance factor when it comes to cycling fast.
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Air resistance rises in a squared ratio with increased speed.
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At a speed of 20 kilometers an hour on a level ground, air resistance has already become the main resistance force.
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And the faster you go, the more air resistance increases exponentially.
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So before even thinking about rolling resistance, get aero.
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Acceleration energy is also expended, for instance, the weight of the wheels is of great importance when this mass has to be brought up to rotation.
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Then when riding uphill, the main resistance force to be overcome is the gradient resistance.
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This is basically the additional resistance added by fighting gravity.
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And in addition to these, there are other friction resistances in the chain, the bottom bracket, and other rotating parts.
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Now, in a well-serviced bicycle, these represent a very minor part of the total resistance.
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So, should you just ignore rolling resistance then?
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Well, no. Because improving your rolling resistance may be the cheapest
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and easiest upgrade you can make to your bike to go faster.
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You can improve all the others by getting aero, by getting a good bike fit and spending the time getting used to it, by getting aerodynamic and light frame,
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by getting some aerodynamic race wheels, and even by upgrading the bearings to maybe ceramic bearings.
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But you can get big gains simply by upgrading your tires and improving your rolling resistance.
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And of course, pumping those tires to the right pressure.
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It's pretty simple.
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A tire with a higher rolling resistance will require more power
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to attain the same speed than a tire with a lower rolling resistance, will require less power.
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So what factors affect the tyres rolling resistance?
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Tyre pressure.
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On a completely smooth surface the following applies.
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The higher the inflation pressure the less the tyre deforms and thus the lower the rolling resistance.
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However on an imperfect surface which we are always riding on lower inflation pressures cause the opposite, lower rolling resistance.
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Imperfections in the road on a very hard tyre will cause bouncing and skipping and increased resistance, not to mention the toll that takes on the rider in terms of fatigue.
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Whereas a tyre with low inflation pressure can adapt better to the rugged surface.
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It sinks into the ground less and absorbs imperfections rather than pushing against them and bouncing off them.
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And so with a softer tyre the whole rotational mass is held back much less on the uneven surface.
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Tire width.
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At the same tyre pressure on a smooth surface a wider tyre will have lower rolling resistance than a narrower tyre.
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This is essentially because a wider tyre with the same pressure actually has an effect of higher pressure
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because a wider tyre with a higher air volume will have a higher casing tension.
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Basically the wider tyre will be harder because it needs more air to fill it and the contact patch, the bit of the tire touching the road, will be smaller and wider, decreasing the rolling resistance.
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But again this only holds true on a smooth surface.
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On an imperfect surface with the pressure corrected for the width to get the tire to the right hardness, the contact patch on the road for a wider tire will be shorter and wider than a narrow tire,
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decreasing the rolling resistance.
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Importantly the wider the tyre will have more versatility and the range of pressures you can actually use, allowing you to more easily correct for the roughness of the surface.
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Tyre construction.
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Obviously the tyre construction has an effect on rolling resistance.
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By using less material, less material can and will be deformed.
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And the more flexible the material is, such as the rubber compound, the less energy is lost through deformation.
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Generally, smoother treads have a lower rolling resistance than rougher treads
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and that is why almost all road
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and triathlon racing tires have very smooth tread patterns
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if any tread pattern at all interestingly actually in racing tires for the road the tread pattern
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that is there is actually not there for grip
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or water dispersion it's mostly there for aerodynamics
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because the tread pattern actually trips the laminar flow as
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that of that air that's hitting the tire to improve the aerodynamics So,
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should you consult a website like BicycleRollingResistance.com where they list all the tested rolling resistance of all tyres
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and simply choose the one from the top of the list?
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Well, yes and no. Yes, the tires on the top of that list will be the fastest.
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However, they're always compromises.
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Some of them may sacrifice durability for that extra speed and be more prone to punctures.
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Some of them may have a different compound that sacrifices comfort
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and grip and road feel and some may simply not work well with your wheel and bike setup.
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It's also worth pointing out that the difference between the top of
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that list of racing tires and the middle of
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that list of racing tires is about a two to three watt saving
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which is an almost imperceptible difference for most mere mortals.
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They will however have a significant difference in those racing tires over your standard training tires.
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So the answer is that the best tire for you depends on many factors
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but it is worth considering investing the $100 to $200 in a good pair of racing tyres.
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It may just be the cheapest watts you buy this season.
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One more thing before we go, you may be asking which is faster rolling resistance-wise, tubeless or clincher?
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Well, the speed of a tyre actually depends on its construction and not whether it's set up clincher or tubeless.
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So, a slow tubeless tyre will actually be slower than a fast clincher tyre.
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However, generally speaking, setup does have better rolling resistance than a tube setup.
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However, if you put a latex tube in a clincher, the rolling resistance is actually the same as tubeless.
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I hope you've enjoyed this video.
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Happy riding!
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本课的词汇与口语要点
这段视频共有 75 个句子、1065 个单词可供跟读。 讲话部分时长为 5:59。 说话人语速自然,每分钟约 178 个词,接近日常对话。 只有 76% 的单词属于英语最常用的 3,000 词,词汇难度较高。
视频中的重点词汇
视频中 15 个值得学习的单词,附发音和释义:
| 单词 | 发音 | 释义 |
|---|---|---|
| tyre 名词 | /taɪə(ɹ)/ | 輪胎 /轮胎, 車胎 /车胎 |
| tire 动词 | /ˈtaɪ̯ɚ/ | 勞累 /劳累, 累 |
| smooth 形容词 | /smuːð/ | 平穩 /平稳, 順利 /顺利 |
| inflation 名词 | /ɪnˈfleɪ.ʃən/ | 通貨膨脹 /通货膨胀, 通脹 /通胀 |
| narrow 形容词 | /ˈnæɹəʊ/ | 窄 |
| tube 名词 | /tuːb/ | 筒 |
| sacrifice 名词 | /ˈsæk.ɹɪ.faɪs/ | 犧牲 /牺牲 |
| bearing 名词 | /ˈbɛɹɪŋ/ | 軸承 /轴承 |
| depend 动词 | /dɪˈpɛnd/ | 信任, 信賴 /信赖 |
| compound 名词 | /ˈkɑmpaʊnd/ | 化合物 |
| decrease 动词 | /dɪˈkɹiːs/ | 減少 /减少, 下降 |
| grip 名词 | /ˈɡɹɪp/ | 柄 |
| width 名词 | /ˈwɪtθ/ | 寬度 /宽度 |
| watt 名词 | /wɑt/ | 瓦特 |
| ignore 动词 | /ɪɡˈnɔː/ | 無視 /无视, 忽略 |
视频中出现的短语动词
| 单词 | 释义 |
|---|---|
| point out 动词 | 指, 指出 |
需要注意的发音
- “th” 音: smooth /smuːð/, width /ˈwɪtθ/, triathlon /tɹaɪˈæθˌlɑn/
- “sh” 和 “zh” 音: inflation /ɪnˈfleɪ.ʃən/, essentially /ɪˈsɛnʃəli/, ratio /ˈɹeɪ.ʃoʊ/, tension /ˈtɛnʃən/, rotation /ɹoʊˈteɪʃən/
- 长单词——注意重音位置: essentially /ɪˈsɛnʃəli/, importantly /ɪmˈpɔɹ.tənt.li/, acceleration /əkˌsɛl.əˈɹeɪ.ʃən/, aerodynamic /ˌɛəɹəʊdaɪˈnæmɪk/, deformation /ˌdɛfəˈmeɪʃən/
如何用这段视频练习
- 先完整听一遍视频,不要开口,记下不认识的单词。
- 先用 0.75 倍速逐句跟读,熟练之后再回到正常速度。
- 录下自己的声音并与原声对比,特别注意 tyre, tire, smooth 这类单词。
视频中的语法
说话人最常用的结构,并附上视频中的原话:
| 结构 | 视频中的用法 |
|---|---|
| 被动语态 be + 过去分词 — 强调发生了什么,而不是谁做的 | is lost · is also expended · be overcome |
| 现在完成时 have/has + 过去分词 — 过去发生但与现在仍有关联的事 | has already become · you've enjoyed |
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。













