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如何赢得自行车比赛:运用齿轮

How to Win a Bike Race: Using Gears

齿轮无处不在 比如在汽车里
Gears are everywhere, incars,
电梯里 甚至自行车里也有它的身影
elevators, even bikes.
如果没有齿轮的参与
None of these objects would work as well
这些物体将无法很好地运作
as they do without the use of gears.
但是我们要怎样理解齿轮的作用呢
But how can weunderstand what gears do?
我们将仔细观察齿轮
We’re going to takea close look at gear
试着弄明白更多关于
and try and understand alittle more the physics
它们原理的物理学和工程学知识
and engineering thatmakes them work.
然后我们将用所学到的去尝试理解
Then we’ll use what we’velearned to try and understand
如何赢得一场自行车比赛
how to win a bike race.
当你准备就绪去参加自行车比赛时
When you’re getting ready for a bike race,
最重要的事是要了解转矩
the most important thing to know about is torque.
转矩由力和距离两个部分组成
A torque is made up ofa force and a distance.
力可以是推力或者拉力
A force is a push ora pull, and that force
它作用在离某点有一定距离的地方
is applied at a certaindistance away from something
这个点我们称之为支点
that we’ll call the pivot point.
注意看 当我试图去推动这个旋转门时
Watch as I try to pushthis revolving door.
推这里很费力 但推这里要容易得多
It’s hard here, butmuch easier here.
为什么会这样呢
Why is that? Well,
当你试图从靠近支点的位置去推门时
when you’re trying to push the door close to the pivot point,
你需要用一个很大的力
you need a big force.
而当你远离支点时
As you move away from the pivot point,
你便增加了转矩中的距离要素
you increase the distance component of the torque.
这样你只需要用更少的力
And then you haveto apply less force.
但其中的取舍是什么呢
But what’s the trade off?
我们来看一下俯视图
Let’s take a look at a top view.
旋转门需要一定的转矩才能转动
This revolving door needs acertain torque to spin around.
你可以获得这个转矩
You can get that torque
通过在离支点很近的位置施加一个较大的力
by applying a big force at a small distance away
或者在支点较远处施加一个较小的力
from the pivot point, or a small force at a big distance. However,
但当你施加一个较大的力时
if youapply a large force,
你只需要转一小圈就可以让它转动
you only need to travel around a small circle to rotate once.
施加较小的力更为轻松 但你需要转一个大圈
Smaller force is easier, but you need to travel in a bigger circle.
齿轮的工作原理和这类似
Gears work in a similar way.
齿轮互相接触 因此 互相传递压力
Gears touch each other, and therefore, apply a force to each other.
齿轮的大小决定了
And the size of the gear iswhat determines the distance
转矩中距离的部分
part of the torque.
一个转矩驱动第一个齿轮
One torque can drive the first gear,
进而在第二个齿轮得到一个不同的转矩
and you get a different torque out of the second gear,
在这种情况下第二个转矩更大
in this case a bigger one.
取舍是什么呢?
The trade off?
较大的齿轮提供较大的转矩
The bigger gearprovides a bigger torque
但不得不绕更远的距离才能转一圈
but has to travel a longer distance before it spins around once.
听起来是不是很耳熟呢
Sound familiar?
自行车使用的叫链轮齿的东西
Bikes use something called a sprocket,
本质上是一个和链条连用的特殊齿轮
which is essentially a special gear for use with a chain.
现在 我们只改变
For now, let’s just say we can only change the size
后链轮齿的大小
of the back sprocket, the one that
它驱动着自行车的后轮
drives the back wheel.
但是怎样改变链轮齿的大小或更换齿轮
But how will changing thesprocket size or shifting gears
才能帮你成为更好的自行车手呢
help you to be a better biker?
为了弄清这个问题 我们将进行一场自行车赛
So to test this out, we’regoing to have a race.
在这场比赛中 我作为第一名骑手
In this race thefirst cyclist, me,
将一直使用大链轮齿
is going to be stuckusing a big sprocket.
第二名骑手将一直使用较小的链轮齿
Second cyclist is going tobe stuck using smaller one.
[音乐起]
[MUSIC PLAYING]
他们出发了
And they’re off.
看起来第二名骑手处于领先位置
It looks like cyclist twois off to an early lead,
此时第一名骑手正猛蹬脚踏板试图追赶
with cyclist one pedalingfuriously to keep up. Oh,
噢 看起来第二名骑手没有充足的转矩
and it looks like cyclisttwo can’t get enough torque
来通过那个斜坡
to get up that hill.
第一名骑手轻松地超过了她
Cyclist one breezes past her.
那么第二名骑手能否在下坡时赶上呢
Can cyclist two catchup on the downhill?
她正在努力
And she does it.
比赛马上接近尾声
It’s going to be a close finish.
第二名骑手获胜了
And cyclist two wins.
正如你所见 当使用较大的链轮齿时
As you could see, usingthe larger sprocket
便是在车轮上施加了一个较大的转矩
let me put a hugetorque on the wheel,
这使我很容易地就上了斜坡
making the hill a piece of cake.
但在其它路段 我都要全力去蹬脚踏板
But to get anywhere, Ihad to pedal my legs off.
就像从离支点较远处去推旋转门一样
Just like moving the revolvingdoor far from the pivot point,
更容易
it’s easier.
却需要移动更多的距离
But there is moredistance involved.
较小的小链轮齿则让第二名骑手可以蹬更多的圈
The smaller sprocket letscyclist two turn the wheel
但由于没有额外的转矩
around many times, butwithout the extra torque,
她上坡时就很费力
she had troublegetting up that hill.
就像从离支点较近处推动旋转门时
Just like moving the doorclose to the pivot point,
更费力 但移动的距离更少
it’s harder, but lessdistance is involved.
希望你现在更加了解齿轮的工作原理
I hope you learned a littlesomething about gears
以及其中蕴含的力与距离的取舍平衡
and the trade offs involved.
我们还有很多要学的东西
There is stillplenty more to learn.
下次再见
See you next time.
[音乐起]
[MUSIC PLAYING]

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视频概述

本文将讲述齿轮的工作原理,以及如何运用这个原理来赢得自行车比赛。

听录译者

收集自网络

翻译译者

猫小葱

审核员

审核员_DB

视频来源

https://www.youtube.com/watch?v=-R0nshBlJXc

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