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撞车物理学

The Physics of Car Crashes

一升汽油所含的能量接近56兆焦
Gasoline has approximately 56 Megajoules of chemical energy per liter , which is more
这比同样数量的TNT爆炸释放出来的能量还要多 这些能量足够
energy than you get from exploding the same of amount of TNT, and is enough to power a
让一台面包机工作一整天 汽车燃烧汽油来使汽油里的化学能转化为
toaster for a full day. Cars work by burning gasoline to convert that chemical energy into
汽车的动能 尽管80%的能量以热能的方式在引擎中流失
the kinetic energy of motion of the car, though almost 80% of it is lost as heat in the engine.
然而 56兆焦能量的20%还是十分多的
Still, 20% of 56 million joules is a lot of joules…
举个栗子来说明汽油能量的转化 大概五汤匙的汽油
To give a direct sense of gas-to-car conversion, it takes about five teaspoons of of gas to
就可以将一辆2吨的汽车加速到60km/h 如果你想保持这个速度
accelerate a 2 ton car to 60kph, and about a third of a cup more for every additional
这将会使每分钟多消耗三分之一杯的汽油
minute you want to keep it going at that speed.
这听起来可能不多 但使一辆车保持60km/h的速度所需能量相当于
That might not sound like a lot of fuel, but the energy of a car moving 60kph is equivalent
将一只大象 或者剑龙Σ(°Д°; 从三楼扔下来
to dropping an elephant – or stegosaurus – from the top of a three-story building.
而且 要使汽车停下来 那么这些能量就需要转移到别的地方 如果刹车的话
And in order for the car to stop, all that energy has to go somewhere. If the brakes
这会通过加热来驱散能量 如果是撞车的话
do the stopping, they dissipate the energy by heating up. In the case of a collision,
能量将通过车外部金属的形变流失 而且
energy is dissipated by the bending and crumpling of metal in the outer areas of the car. And
就像慢慢刹车比急刹舒服 汽车被小心翼翼的设计
just like how smooth braking is nicer than a quick jerky stop, cars are carefully designed
成耐形变的形态 当它们相撞时 这种设计加长了形变的时间
to crumple – when they crash – in a way that lengthens the duration of the impact so that
而停下来的加速度将会更小 如果速度改变过快的话
stopping requires less intense acceleration. Lots of acceleration over a very short time
对人类柔软的大脑和器官可不太好
is not good for soft human brains and organs.
但是 人们不喜欢带着匹诺曹的鼻子开车 所以大部分的车
However, people don’t like driving cars with Pinocchio-length noses, so most cars
只有大概50cm的碰撞缓冲区域来使小剑龙掉下来๛ก(ー̀ωー́ก)的能量流失
only have around 50 cm of crushable space in which to dissipate the energy equivalent
这意味着 当车形变时 引擎周围的空间需要抵抗
of our falling stegosaur. That means that, while crumpling, they need to maintain a resistive
大约四分之一的撞击力 超过一半
force of about a quarter the thrust of the space shuttle main engine. Over half of the
的形变通过汽车里的缓冲器完成
controlled-crumpling work is done by a pair of steel rails connecting the front bumper
缓冲器可以通过弯曲变形来吸收能量 使车减速 剩余的大部分能量
to the body, which bend and deform to absorb energy and slow the car. Most of the rest
被车头其他形变
of the energy is absorbed by the deformation of other pieces of structural metal throughout
的金属吸收
the front of the car.
这种设计使人们在撞车的时候获得巨大但
This meticulously engineered destruction allows a crashing car to decelerate at a high but
还可以接受的加速度 仅仅比宇航员或飞行员在离心训练时的加速度
reasonable rate: just slightly over the acceleration experienced by fighter pilots or astronauts
大一丢丢 相比较 如果汽车的车身炒鸡坚硬(就像在50年代以前)
in centrifuge training. As comparison, if cars were super rigid (like they were before
不会形变的话 它们会超级快的停下来 人们会获得
the 1950s) and didn’t crumple, they would stop so fast that they would undergo acceleration
飞行员离心训练获得加速度的15倍的加速度 幸好设计家们会
15 times what fighter pilots experience in training. Thankfully engineers have learned
在车上设计出缓冲空间 因为完全坚硬的
to make cars with crunchy crumple zones surrounding their rigid safety cell, because fully rigid
车身对飞行员或者其他人可不好 唔 机器人除外
cars are not good for fighter pilots or anyone else. Except, maybe, robots.
这集分钟物理由福特赞助播出 我在这里感谢一个
This MinutePhysics video was made possible by Ford – I was able to talk to an awesome
指导我这些复杂的物理学和工程学的专注改善汽车设计的
crash test safety engineer there who told me all about the complex physics and engineering
炒鸡腻害的工程师
that goes into vehicle development and improving how cars perform in a crash.
福特给了我这次机会 因为它想你意识到汽车的设计
Ford gave me this opportunity because they want you to know how important and carefully
是有多重要 而使用汽车测试
designed all the parts involved are, and in particular that the only parts developed and
是由福特汽车开始的哟
tested to work with their vehicles are original Ford parts.
如果你想学到更多的话 你可以戳takeagoodlook.com
If you want to learn more about why the right parts matter, you can head to takeagoodlook.com.
个人来说 这部视频加强了我的意识
And I personally want to say that making this video has just reinforced to me that regardless
不管你开什么车 车身上的花纹和变形不仅仅是因为美观
of what kind of car you have, big dents and deformations in the body aren’t just aesthetic
它们可以保护你
problems – they can be safety hazards, too.

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