smart in any particular field you have to go talk to the experts. This is why I went

在任何一個特定的領域，你必須去跟專家交流。 這就是為什麼我去

to Germany to a guy named Jörg Sprave. [thunder] Now today we're gonna learn about

到德國一個叫Jörg Sprave的傢伙。[雷霆]現在，今天我們'要去學習關於

the physics of slingshots but before we do that, let's just have some fun shooting.

彈弓的物理學，但在我們做之前，讓'我們只是有一些有趣的射擊。

You're getting Smarter Every Day.

你每天都在變得更聰明。

So today we are in Germany at a 300 year old dairy farm in a small village.

所以，今天我們在德國的一個小村莊裡的一個有300年曆史的奶牛場。

Jörg, so what are we gonna do? - Well we're gonna see Tobias

約格，我們要做什麼？- 好吧，我們要去看托比亞斯

shooting, and Tobias is actually the current world record holder for the

射擊，而托比亞斯實際上是目前世界紀錄的保持者，他的射擊成績是

strongest handheld slingshot, so getting more than a hundred joules

最強的手持彈弓，所以獲得超過一百焦耳的能量。

with the handheld slingshot. So we're gonna try to kill this good German beer.

與手持彈弓。 所以，我們'要去嘗試殺死這個好的德國啤酒。

We've been shaking this a bit. Let's hope for the best.

我們'一直在搖晃這一點。讓我們'希望最好的。

[cheering]

[歡呼聲]

Oh man.

哦，天啊

[laughing]

[笑]

Ja. That's the way.

賈。就是這樣。

[music]

[音樂]

[laughing] Oh man.

[笑]哦，夥計。

(Jorg) It's really dark red love the color. (Destin) Arrgh it looks like a skull.

它真的是深紅色的 喜歡這個顏色 It's really dark red love the color.看起來像個骷髏頭 Arrgh it looks like a skull.

It's pretty wild (Destin) It is dark red.

它'很野（Destin）它是深紅色的。

(Destin) Awesome. High five! We give high fives in America.

太棒了擊掌！在美國我們要擊掌。

[laughs] High five Jörg. Nice.

[笑]擊掌Jörg。很好。

Elastic is a pretty interesting material.

彈性是一種相當有趣的材料。

Alright so here's our graph. So if we want to add energy to the system,

好吧，所以這裡'是我們的圖。 所以，如果我們想增加能量的系統，

meaning increase the potential energy on the bands of the slingshot,

意味著增加彈弓帶上的勢能。

all you have to do is pull back the bands, obviously. But the thing

你所要做的就是把帶子拉回來，很明顯。 但問題是

about this is when you pull the bands back, the further you pull the more difficult it

當你把帶子往後拉的時候，你越拉越困難

gets to pull. Let me show you. If you look at this force gauge the further I pull

得到拉。讓我給你看看。 如果你看這個測力計，我拉得越遠...

the more difficult it becomes. If I were to plot the

越是困難。 如果我繪製的是

potential energy going into the system versus the displacement as I pull back,

進入系統的勢能與我拉回時的位移。

because it gets harder it's not a linear graph, it's actually a curved function.

因為它越來越難它'不是一個線性圖形，它'實際上是一個曲線函數。

So here's something else. As I release the projectile and then it begins to accelerate

所以，這裡'是別的東西。當我釋放彈丸後，它開始加速。

out of the pouch down towards the fork, it's going to also

袋子裡的東西向叉子裡放，它也會向叉子裡放。

have this curved function because of the material properties there, but here's

有這種曲線函數，因為那裡的材料屬性，但這裡'的。

the interesting part. If you were to add up the potential energy still left

有趣的部分。 如果你把剩下的勢能加起來的話 If you were to add up the potential energy still left

in the band, and the kinetic energy of the projectile going towards the fork

在帶狀物中，彈丸的動能向分叉方向移動。

at any point along the displacement going back towards the fork, they would equal

沿著位移向叉子方向的任何一點，它們將等於

approximately the total energy that I put into the system. OK the last

大約是我投入系統的總能量。 好了，最後一個

property of elastic I didn't understand until I saw some of Jörg's experiments. As you pull the bands

彈性的屬性，我沒有'理解，直到我看到一些Jörg'的實驗。當你拉動帶子的時候

back they heat up. But if you hold them there and allow them to cool off,

後面他們會熱起來。但如果你把它們放在那裡，讓它們冷卻下來。

you're losing energy. So what this means is the total potential energy

你'正在失去能量。 所以這意味著總勢能

in the system is going to go down, so your projectile will be slower if you

系統中的能量會下降，所以你的彈丸會更慢，如果你

sit there and wait and let your bands cool off. Why do you think that happens?

坐在那裡等待，讓你的樂隊冷卻下來。 你覺得為什麼會這樣？

Jörg you want to explain it a little bit? (Jörg) Yes. Tobias' record shot

約爾格 你想解釋一下嗎？（約格）是的。托比亞斯' 記錄拍攝

was shooting a 20mm steel ball at 83m/s

以83米/秒的速度射出20毫米的鋼珠。

which is 115 joules. (Destin) OK ready.

這是115焦耳。(Destin)OK準備好了。

(Jorg) How he acheives that is by

他是如何做到這一點的呢？

drawing out and firing immediately without any kind of break,

拔出並立即開火，沒有任何形式的中斷。

so that the rubber is still at full force and it doesn't lose

以使橡膠仍處於全力以赴的狀態，而不會失去'。

power through the hysteresis that otherwise happens.

功率通過滯後，否則會發生。

Oooh! [laughing]

哦！ [笑]

(Destin) Good grief. How thick is this?

(Destin) Good grief.這有多厚？

Oh yeah.

哦，是的。

This is a Frustum. A frustum is when you try to distribute a stress throughout a material.

這是一個結殼。殼是指在材料上分佈應力。

OK here I have two bands and they're C-clamped to the barn, and as I go down the length of

好吧，在這裡，我有兩個帶子，他們&#39；C夾到穀倉，而當我去了長度的

the band you can see the one on the left is tapered to a smaller width than the one on the right.

你可以看到左邊的那條帶子比右邊那條帶子的寬度要小。

So clearly if I put weight on each of them,

所以很明顯，如果我把重量放在他們每個人身上。

then the one on the left you would assume would stretch more because it has less material

那麼左邊的那個你會認為會拉伸更多，因為它有較少的材料。

resisting the stretch right? OK yeah, that makes sense.

抵抗拉伸吧？好吧，是的，有道理。

So if we were to fire a slingshot with both a tapered band and an untapered

所以，如果我們要發射的彈弓既有錐形帶，又有非錐形帶。

band, I would assume that the one on the right, the untapered band would

帶，我認為右邊的那個，未錐化的帶子應該是。

accellerate the projectile faster right? No. That's not what happens

是的，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，我的意思是，

at all. And the slingshot community has known this for years but they never had the rock solid evidence.

根本沒有。而彈弓界多年來也知道這一點，但他們始終沒有得到確鑿的證據。

So that's what Jörg and I did with the Phantom high speed camera. We fired

所以，這'是什麼約格和我做了與Phantom高速攝影機。我們發射了

two different slingshots at 1000 frames per second. The one on the top here

兩個不同的彈弓，每秒1000幀。這裡最上面的那張

is an untapered band, the one on the bottom is a tapered band. The top band

是一個非錐形帶，底部的是一個錐形帶。頂部的帶子

is clearly accellerating slower than the bottom band.

明顯比底部波段加速慢。

My theory is pretty simple. Every solid material has what is called a stress strain curve

我的理論非常簡單。每一種固體材料都有所謂的應力應變曲線。

Stress is the force per unit cross sectional area on the material as you pull it.

應力是指在拉動材料時，材料上組織、部門橫截面積所受的力。

Strain is the percentage that it elongates as you pull it.

應變是指當你拉動它時，它伸長的百分比。

You are probably putting more strain energy into the system.

你可能把更多的應變能量放到了系統中。

OK in summary, we went to two different continents, I learned two things and I'm gonna

好吧，總之，我們去了兩個不同的大陸，我學到了兩樣東西，我'會

ask you two questions. First thing I learned. The potential energy in a stretched

問你兩個問題。第一件事我知道了。伸展的勢能

rubber band is conserved, however it is rapidly dissipated in the form of heat.

橡皮筋被保存下來，但它會以熱量的形式迅速散失。

The second thing, for slingshots a tapered band is more efficient or effective at

第二件事，對於彈弓來說，錐形帶的效率更高，或者說效果更好。

converting potential energy into kinetic energy. Here's a little bonus.

將勢能轉化為動能。這裡'是一個小小的獎勵。

In 1660 a guy named Robert Hooke discovered the law of elasticity, or

1660年，一個叫羅伯特-胡克的人發現了彈性定律，或者說是...

Hookes Law. Here's the interesting thing. The rubber in

鉤子法。這裡'是有趣的事情。橡皮在

a rubber band does not obey the law of elasticity. I'll leave a link

橡皮筋不服從彈性定律。我留下一個鏈接

in the description so you can read about that, but spoiler alert, some of your physics books might be wrong.

在描述中，所以你可以閱讀有關，但擾亂警報，你的一些物理書可能是錯誤的。

Anyway, here's the two questions for you. Number one. Why does rubber

總之，這裡有兩個問題要問你。第一個問題。為什麼橡膠

lose energy when it cools off? I.e. I can shoot a rubber band farther

冷卻後會失去能量？即我可以把橡皮筋射得更遠。

if I just pull it back and let it go. And the second thing, why are tapered bands more efficient?

如果我只是把它拉回來，讓它去。第二件事，為什麼錐形帶的效率更高？

Help me figure this out. I'm Destin. Thank you very much for watching.

幫我搞清楚我是Destin非常感謝你的觀看。

Enjoy the outtakes.

欣賞一下這些花絮。

Jorg's really good, and I wanted to go from a superficial

Jorg'的真的很好，我想從一個膚淺的。

knowledge about how elastic works to a deep understanding. But before we look into the physics

彈性工作原理的知識進行深入瞭解。但在我們研究物理學之前

of slingshots... let's just shoot. I just messed that up.

的彈弓... ... 讓我們只是拍攝。我只是搞砸了。

even though I hit it. Blah! We're using less reactive

即使我打它。Blah!我們用的是不太活躍的

material to fire something faster [goat bleating] Come on in.

材料發射的東西更快 [山羊咩咩叫] 進來吧。

Come on in.

進來吧

...talk about slingshots. I wanted to learn...

...談論彈弓。我想學習...

[whispered] oh no.

[耳語]哦，不。

When I first saw you I

我第一次見到你的時候

though you were kind of a sissy so I'm glad to see that you're not. [laugh]

雖然你是個娘娘腔，所以我很高興看到你不是。[笑]

I'm only talking like this because his hand is

我之所以這樣說，是因為他的手是

hurt and he can't punch me.

傷，他不能打我。

...so I wanted to go from a deep...

...所以我想從一個深... ...

I'm killing myself here. I can't talk.

我在這裡殺了自己。我不能說話。

...tapered one actually deflects more. But here's the interesting part. It.. goat.. really.

......錐形的其實更偏向於。但這裡有一個有趣的部分。它... 山羊... 真的。

... I wanted to learn about the elasticity of...

...我想了解一下彈性... ...

Aah!

啊！

...Jörg Sprave [thunder] Now today we're gonna learn about the physics of slingshots but

...Jörg Sprave ...Now today we're gonna learn about the physics of slingshots but...

before we do that, let's just have some fun shooting. You're getting Smarter Every Day.

在我們這樣做之前，讓'我們只是有一些有趣的拍攝。你每天都在變得更聰明。

I finally said my words right!

我終於把我的話說對了!

Now that the lightning's here. [laugh]

現在，閃電在這裡。[笑]

[ Captions by Andrew Jackson ] captionsbyandrew.wordpress.com

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