energy than you get from exploding the same of amount of TNT, and is enough to power a

這比引爆等量的TNT(黃色炸藥)釋出的能量還要多 或者足夠讓一台

toaster for a full day.

烤土司機運作整天 車子就是靠著燃燒汽油來把其中的化學能

Cars work by burning gasoline to convert that chemical energy into the kinetic energy of

轉換成車子的動能 儘管幾乎八成的能量在這個過程中以熱的形式散失掉

motion of the car, though almost 80% of it is lost as heat in the engine.

但5600萬焦耳的兩成還是很多焦耳...

Still, 20% of 56 million joules is a lot of joules…

如果要給出一個比較直覺的對比 5茶匙的汽油可以讓一台

To give a direct sense of gas-to-car conversion, it takes about five teaspoons of of gas to

2噸的車從靜止加速到60km/hr 而每多出1/3杯就可以讓這台車子

accelerate a 2 ton car to 60kph, and about a third of a cup more for every additional

繼續用同樣的速度跑1分鐘

minute you want to keep it going at that speed.

這可能聽起來不是很多 但一輛以60km/hr前進的車所擁有的能量相當於

That might not sound like a lot of fuel, but the energy of a car moving 60kph is equivalent

把一隻大象(或劍龍)從三層樓高的地方丟下來

to dropping an elephant – or stegosaurus – from the top of a three-story building.

而且如果這輛車要停下來 那些能量全部都要跑去別的地方

And in order for the car to stop, all that energy has to go somewhere.

如果是煞車讓車子停下來 能量會被用來產生熱 但如果是碰撞讓車子停下來的話

If the brakes do the stopping, they dissipate the energy by heating up.

能量則會被用來折彎和壓扁車子外面的金屬

In the case of a collision, energy is dissipated by the bending and crumpling of metal in the

就像慢慢的煞車比緊急煞車來的舒服一樣 車子就是被設計成

outer areas of the car.

出車禍的時候會被壓爛 藉以延長受衝擊的時間

And just like how smooth braking is nicer than a quick jerky stop, cars are carefully

所以停下來所需要的加速度會比較小 在一小段時間裡突然受到很大的加速度

designed to crumple - when they crash - in a way that lengthens the duration of the impact

對我們柔軟的腦袋和器官不是很好

so that stopping requires less intense acceleration.

然而 大家都不喜歡開跟小木偶的 鼻子一樣長的車子 所以大部分的車

Lots of acceleration over a very short time is not good for soft human brains and organs.

只有大概50cm可以被壓爛的空間來吸收 跟一隻掉下來的劍龍一樣多的能量

However, people don’t like driving cars with Pinocchio-length noses, so most cars

也就是說 在整個被壓爛的過程裡 它必須要保持相當於1/4倍

only have around 50 cm of crushable space in which to dissipate the energy equivalent

太空梭主引擎推進力的阻力 超過一半的力道是由

of our falling stegosaur.

一對連接著保險桿和車身的鋼軌

That means that, while crumpling, they need to maintain a resistive force of about a quarter

彎曲變形之後吸收 並讓車子減速 剩下的能量

the thrust of the space shuttle main engine.

大部分是由車頭的其他金屬

Over half of the controlled-crumpling work is done by a pair of steel rails connecting

所吸收掉

the front bumper to the body, which bend and deform to absorb energy and slow the car.

這種精心設計的破壞使得一輛出車禍的車 能夠以雖大但尚能接受的

Most of the rest of the energy is absorbed by the deformation of other pieces of structural

加速度停下來: 稍微比戰鬥機飛行員或 接受離心訓練的太空員所體會的

metal throughout the front of the car.

加速度再大一些 相較之下 如果車子本身超級堅硬而且不會被壓爛

This meticulously engineered destruction allows a crashing car to decelerate at a high but

(像是1950年代前的車子) 它們就會停得太快 以致於它們會體會到相當於戰鬥機飛行員

reasonable rate: just slightly over the acceleration experienced by fighter pilots or astronauts

在訓練時所感受的加速度的15倍 這對你的器官絕對不是很好 幸好工程師們

in centrifuge training.

已經學會製造受酥脆金屬皮包覆 裡面還有著堅硬金屬籠的車子 畢竟完全堅固的

As comparison, if cars were super rigid (like they were before the 1950s) and didn’t crumple,

車子對戰鬥機飛行員或任何其他人來說都不太好 除了 呃 機器人之外

they would stop so fast that they would undergo acceleration 15 times what fighter pilots

experience in training.

Thankfully engineers have learned to make cars with crunchy crumple zones surrounding

their rigid safety cell, because fully rigid cars are not good for fighter pilots or anyone

else.

Except, maybe, robots.

This MinutePhysics video was made possible by Ford - I was able to talk to an awesome

crash test safety engineer there who told me all about the complex physics and engineering

that goes into vehicle development and improving how cars perform in a crash.

Ford gave me this opportunity because they want you to know how important and carefully

designed all the parts involved are, and in particular that the only parts developed and

tested to work with their vehicles are original Ford parts.

If you want to learn more about why the right parts matter, you can head to takeagoodlook.com.

And I personally want to say that making this video has just reinforced to me that regardless

of what kind of car you have, big dents and deformations in the body aren’t just aesthetic

problems – they can be safety hazards, too.