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  • Hey it's me Destin. Welcome back to Smarter Every Day. Today we're gonna do awesome science with

  • Orbix Hot Glass here at Lookout Mountain Alabama. Goggle up.

  • Science is about to happen. We're gonna use a high speed camera and learn about Prince Rupert's Drop.

  • [whispers] It's never been done on the internet. You're gonna learn something.

  • Let's go.

  • OK we are here inside the shop with

  • Cal. Cal owns the place. Can you show me how to make a Prince Rupert's Drop?

  • (Cal) Sure. I'm gonna gather some glass, drop it in a bucket of

  • cold water.

  • [sizzling sound]

  • (Destin) So after it cools down, this is what you're left with.

  • It kinda looks like a tadpole, but it has some really interesting mechanical properties.

  • We can actually hit this thing with a hammer and it won't break.

  • OK I'm ready. [bang] Didn't go.

  • OK I think Cal is kind of a pansy so I.. You think you can break it? [laugh]

  • So we're gonna try again only this time I'm gonna make him hit it really hard

  • and I'm gonna record it with high speed. Does that work? Think you can break it? Alright. Let's do it.

  • The challenge is on. (Cal) Just hit it? - Yep.

  • [bang] [shattering] [laughs] So do you think you actually broke it? I don't think

  • you did. You think you broke it? - I know I broke it. [laugh]

  • - Let's look at the high speed.

  • [music]

  • OK so the drop broke, but technically it wasn't the

  • hammer that broke it. If you look close in the high speed you can see that it's the wiggling of the

  • tail that makes it go. This is the mystery of the

  • Prince Rupert's Drop. You can try

  • as hard as you can to break the bulb, but you can't.

  • But, if you even nick the tail, the entire thing will explode. Not shatter,

  • but actually explode. Let's go outside and I'll show you more.

  • OK we're gonna just run an obscene frame rate here. We have this

  • Phantom V1610. So, glass breaking occurs

  • so fast that you have to have like hundreds of thousands of frames per second, so we're gonna

  • have a lower resolution and we have to have a lot of light as well. We're also gonna use this Miro over

  • here to run about 3000 frames per second so we can get a wide shot to see the whole event.

  • as well. 3..2..1.. go.

  • [shatter]

  • [Awesome Music by Gordon McGladdery}

  • OK now we understand what a Prince Rupert Drop does, but at this point

  • we don't quite understand why it does it. Let's take a closer look.

  • OK this is called a polariscope and basically what it is is it's a filtered piece of

  • glass that's polarized. I have another filter here. You can see if I turn it,

  • then I can block out the light. Now if I put this on the camera

  • that you're looking through here, and then I put the Prince Rupert's Drop in between

  • the two pieces of glass, you should be able to see the internal stresses built up

  • inside the Prince Rupert's Drop. So to understand how these stresses got here, let's

  • use the color grey to represent nice and strong solid glass. We use red

  • to represent molten glass and because of the thermal expansion coefficient it's safe to assume that the

  • higher the temperature the larger this glass wants to be. Blue represents glass that's cooling

  • off, or transitioning between the two states. Because of that same thermal expansion coefficient

  • this glass is shrinking and basically pulling in on itself. Think of a

  • Prince Rupert's Drop as a bunch of little infantessimal pieces of glass with each piece trying to interact

  • with the pieces around it. When the molten glass is first dripped into the water, the

  • outside layer touches the water and immediately solidifies. This locks in that

  • outside shape of the drop. The inside of the drop however is still a hot expanded

  • liquid. As heat's transferred to the water that glass on the inside slowly begins to

  • cool down, and pulls in against that outside layer. The problem is that

  • because it's already locked in as a round solid, it only compresses tighter against

  • itself. This actually makes it stronger. Kind of like how an arch compresses and gets stronger when

  • you put your weight on it only this is in all directions. And because the cooling glass can't

  • move that outside layer it begins to pull against itself, causing it to be

  • in extremely high tension. It then hardens in this state of tension and there you have it, a

  • Prince Rupert's Drop. The outside is in extremely high compressive stress and the inside is in

  • extremely high tensile stress. If one link in this tension chain is ever cut, it

  • breaks on down the line, feeding off of its own stored up energy just like a chemical

  • explosive does. The difference here is that instead of releasing chemical potential energy

  • mechanical strain energy is released. This wave of energy is what we call a

  • failure front. You can directly measure the velocity of that failure front as long as

  • you have a camera fast enough. Let's give it a shot at 130,000 frames

  • per second. 3..2..1..go.

  • Got it?

  • [music]

  • So a big thanks to Cal from Orbix Hot Glass. If you found this

  • interesting and you want to support him by buying stuff go click on the link, wherever I

  • put it, and go check out his web site. Click the cat to subscribe.

  • With the helmet. [laugh] It's a sad looking cat.

  • You've never caught the cat on fire, ever? - Never. - Not even once?

  • - Never. - These things are named for a guy named Prince Rupert, imagine that,

  • who lived in Bavaria back in the 1600s. Here, here.

  • [shins banging on concrete laughter through pain]

  • He brought these over as a gift to King Charles II in England who gave them to his

  • Royal Society to try to figure out. Yep ready. [clang]

  • Holy smokes!

  • - Aah the tension's killing me. [shatter] -(Destin in background) NO DON'T BLOW UP!

  • - You know it blow.. blowed up? - Yep, it blowed up.

  • - It BLOWED UP Y'ALL! [laugh]

  • Captioning in different languages welcome. Please contact Destin if you can help.

  • [ Captions by Andrew Jackson ] captionsbyandrew.wordpress.com

Hey it's me Destin. Welcome back to Smarter Every Day. Today we're gonna do awesome science with

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Mystery of Prince Rupert's Drop at 130,000 fps - Smarter Every Day 86

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    起鳳 posted on 2013/08/01
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