All great inventions.

都是偉大的發明。

But for me, the most important of all

但對我來說，最重要的是

was the wheel, mainly because it led to things like this.

是車輪，主要是因為它導致了這樣的事情。

Downhill cycling.

下坡自行車運動。

Why use two wheels when one makes you look twice as cool?

為什麼要用兩個輪子，一個輪子就能讓你看起來更酷？

But before you even think about pulling off a downhill wheelie,

但在你還沒有想好要不要來個下坡輪滑之前。

be aware that even on two wheels,

要知道，即使在兩個輪子上。

it could still be perilous.

它仍然可能是危險的。

What makes downhill cycling is such a terrifying pursuit

是什麼讓下坡自行車運動成為一種可怕的追求？

is that the bike isn't only powered by the cyclist's legs,

是自行車的動力不僅僅是靠騎車人的雙腿。

but also by our old friend gravity.

但也被我們的老朋友引力所影響。

When a cyclist goes up a hill, he gradually gains

當一個騎自行車的人上坡時，他逐漸獲得了

gravitational potential energy.

引力勢能。

When he descends, this gravitational potential energy

當他下降的時候，這個重力勢能

can be converted over a very short period of time

可以在很短的時間內完成轉換。

into a terrifying amount of kinetic energy.

化為可怕的動能。

If the rider falls, that kinetic energy might be converted

如果騎手摔倒，那動能可能會被轉化為

into heat via friction, or if they stop suddenly,

通過摩擦轉化為熱量，或者如果它們突然停止。

dissipated via deformation.

通過變形耗散。

So energy is never destroyed.

所以能量永遠不會被破壞。

It's merely transferred into something else

只不過是轉移到了別的東西里

like kinetic energy, heat, or even the sound

如動能、熱能、甚至聲音等。

of an impact, which is often accompanied

的影響，往往伴隨著

by the sound of screaming.

由尖叫聲。

To investigate, we sent out some of our more

為了調查，我們派出了我們的一些更多。

reckless researchers.

魯莽的研究人員。

This guy has made a deal with gravity

這傢伙已經和地心引力做了交易

and built up a lot of kinetic energy.

並積累了大量的動能。

So much so that he's able to pass cars.

以至於他能夠超越汽車。

Except that one.

除了那個。

The cyclist is unable to transfer

騎車人無法轉移

enough kinetic energy into heat the friction at its brakes.

足夠的動能轉化為熱量在其剎車處摩擦。

When he hits the car, his remaining kinetic energy

當他撞上汽車時，他剩餘的動能... ...

is transferred into sound, heat, and dissipated a deformation,

被轉移到聲音、熱量，並消解了變形。

also known as bouncing off.

又稱彈開。

Don't worry.

別擔心

He was OK.

他還好。

All right.

好吧，我知道了

Let's try a gentler pace.

讓我們嘗試一個更溫柔的步伐。

This is more like it.

這是更喜歡它。

A chance to take in the scenery.

一個欣賞風景的機會。

And his friend's bottom.

還有他朋友的底子。

He appears to make no attempt to reduce his kinetic energy.

他似乎沒有做出任何減少動能的嘗試。

And his linear momentum becomes angular momentum

而他的直線動量變成了角動量。

as he rotates around the axle of the front wheel.

當他繞著前輪軸旋轉時。

And maybe not the last.

也許不是最後一次。

Perhaps it's safer to go downhill on three

也許三下五除二的下山比較安全吧。

wheels with these drift trikes.

這些漂移三輪車的車輪。

Or maybe not.

也可能不是

It's just as well our drift trike gang are

正好我們的漂移三輪車團伙是

heading home on four wheels.

用四輪車回家。

Maybe safer just to walk.

也許走著走著就安全了。