## Subtitles section Play video

• Hello there, I'm Gav. I'm Dan. We're the Slow Mo Guys. This should be a nice simple video. How fast does glass crack?

• I actually don't know but we did that one video with the Pyrex jug where we saw it

• Yeah, but it was actually quite difficult to figure out the speed because the, the crack was going through a curved

• Pyrex jug handle. It was about this big. It's almost like we need a really long piece of glass with foot markers on it.

• Where could we, uh, get one of those, do you think?

• Oh! Oh, here's one. Look at this. I wondered what this was doing here.

• So in theory if we break this at one end the crack should rush through it

• I'm gonna put foot lines on it and we'll be able to determine the exact speed of a glass break

• What I've done here with our 7-foot piece of glass is I've spray-painted exactly a foot along the glass

• Now a foot's gonna start at, from the cameras point of view the left-hand side of the blue

• So this edge is gonna be exactly a foot from here. And this one's gonna be exactly a foot from here, etc

• So you should be able to calculate the exact speed

• For glass as we know we need very high speeds.

• The Phantom Flex4K only does a thousand frames a second.

• Not worth it.

• Might seeit'd be couple of frames, maybe, if that.

• We've got the "Twenty Five Twelve" here today. We usually use the "Twenty Five Eleven"

• This is the next revision

• Has a different CineMag and a much bigger internal memory. But other than that, it's the same camera

• So we'll start at 28,500 frames a second.

• A bit nerve-racking, this. Oh, yeah, you're telling me!

• Right. You stand there.

• A bit of foam I see you've got there for protection.

• Yeah, you've gotta protect the glassotherwise it'll smash before we're ready.

• *gasp*

• Cool. So I'll hold it here. Okay, you got it? I think so.

• I'm gonna bug in a ton of shutter here 45 degrees. Oh that's noise. You never do that. Why do you know in it?

• Let me just grip this with this and see if I can smash the glass with just a pair of pliers, babe. Go for it

• That works not really what Oh just vanished God I didn't expect to be able to do that and then he just went oh

• You really framed up on the edges aren't you yep three two one step oh

• Cool that's really no I'm surprised you can even see that much with the 28,000. Yeah, it's because it's so big

• This is our starting frame rate. We plan on going much faster. I also like the fact that if I speed up a bit

• it's like

• irrelevant of gravity it splits up and down at the same time because I guess the pressure being released just goes with

• It also shot forwards and at me once it when you crack it it sort of explodes

• Yeah, that's why it makes that like sort of sound or it pops because it like has the pressure built up

• I guess I did this with pain instead of tape. Oh

• Yeah, yeah, you could see it separating. You can actually kind of see where everything was even in the air

• It stays jagged directly in line underneath each other

• Faster oh, yeah

• so the way you can increase the framerate on the phantom cameras is you just lower the resolution and

• As you may have noticed the top on the bottom of the frame here a complete

• Garbage nor a waste. So what I can do is keep the width the same but lower the vertical resolution

• So maybe something like that and that way we're keeping all of the useful area

• But it will give us the chance to go to

• Yep, 63 get some a darker. Probably not much sure to compensate

• Should be

• So this time I'll get some different colors in the go

• Yeah, I'm gonna start by spraying each foot marker with a different color painting with den. Yeh

• I'm just gonna get on the table here are in a rush. They

• That's read done I like that you're doing this across two tables so you rank both at once I won't

• Enjoy that

• Lovely so the right-hand side of these or your left will be a foot long. This is pretty satisfying

• Slop it in there

• When you get a chance, okay, let me try and fill the frame with this mad lad go for it my level

• Okay, Dan, it's time for some maths

• Versus I'm gonna get up the true

• Time of this crack and we'll measure how long in seconds it took each foot to break

• There's a slight discrepancy between each one just because of which side of the foot mark of the crack landed on that particular frame

• But don't worry will a ver each term out more Matt

• Giving us average time of point zero zero two

• seconds per foot which is forty seven hundred and fifty eight feet per second and for the international audiences, that's

• 1,450 M years per second

• 3262 miles per hour

• 5250 km/h or mac

• 4.20

• You know, my mind is blown. I don't think that there's anything that's like physical but that's quick

• What's physical that that's quickly? What goes Mac 4.2 apart from spaceship?

• It's almost it's weird how like none of it overtakes anything else like, okay so it starts as round right?

• See that it's not rounded. Yeah, so the middle of the glass is actually ahead of the sides

• But it catches up and then it's all just going in a line. Do you know I think

• Right, that is not I don't expect to see there

• I think it what it looks like is if this was actually a circle like if it was like a 14

• Foot circle. Yeah, and you smashed the middle it would all go out in a circle

• But we're just seeing like a section of that. So if you imagine that

• It starts off as a small circle it gets bigger and bigger. It doesn't it's not actually flat when he gets the end

• It's still slightly curved. So I'm just imagining a circle getting bigger. Therefore. The edge is getting flatter. Yeah, exactly

• bloody

• Mental now can't want to do it a big circle

• fresh out of

• 14-foot glass circles, unfortunately good church window

• alright, so that was

• 78,000 multi-coloured. Yeah, I think it's time to get carried away

• This bad boys the capable of some serious, let's Lincoln. Let's let it stretch this legs

• Thank you every spin

• Will reduce the horizontal width as well

• Lose some more on the vehicle

• maybe go

• To five six by

• Ninety six, that's small enough giving us a frame rate over four hundred and eighty one and a half

• Thousand frames a second because we're now so cropped in

• I'm only gonna be seeing two colors. So there's no point painting the rest waste the paint waste a paint

• Glass is cool Oh

• Ridiculous, how much can you see bloody stupid? This is

• She's that one pot? Let's look at this ridiculousness

• It just looks like a software wipe

• it's just like we took two fixes then just wiped across it just instantly turns it to like lizard skin just turns into like

• Scales this cameras. So cool just records all that like that happened and it recorded it at that. Yeah this camera saw everything

• final aftermath

• Another pretty aftermath that is not bad. It sounds like snow - listen

• Don't like snow but what's cool is the fact that cuz obviously we did it all in in color order. It's all stayed there and

• Look, this is all

• This looks like it's an intact piece of glass but it's actually oh, yeah, at least smash it's gone

• It's just held together by there. Yeah, which is why it was good that lab

• We didn't record the the paint side who recorded the front side so you can see the cracking around the color

• Well, we learned the speed that a crack propagates through laminated sheet of glass

• Yeah, they've temp in action. You couldn't tell with the the little video we did before but that really demonstrated

• It was so fast

• and and the way it starts as a circle and then basically gets

• Bigger for in a circle, even though it's a flat rectangular piece of glass. I was really impressed by that

• I didn't I didn't expect to see that

• I guess you'd never know it unless you see a long piece of glass slow motion in my head

• You were gonna crack it and it would just come across as a straight ball the whole way of outside

• Oh, of course. It's gonna crack from that point and then the fact that it evened out was very cool to me

• Yeah, it was awesome

• Hopefully you enjoyed that video bung it alike. If you did, there's a dislike button - that's always fun. Subscribe to the slow

• Mo guys and we've got a second channel any closing thoughts Daniel gets a bear get a broomis will get a get a broom

• Yep for this got this grass

• Glass grass grow I met grass that time. Okay. Yeah because I'm gonna sweep up the glass from the grass

• Yeah

Hello there, I'm Gav. I'm Dan. We're the Slow Mo Guys. This should be a nice simple video. How fast does glass crack?

Subtitles and vocabulary

Click the word to look it up Click the word to find further inforamtion about it

# How fast does glass crack? - The Slow Mo Guys

• 1 0
林宜悉 posted on 2020/03/19
Video vocabulary