Windows Exploding: Science Behind the Scenes

[nacho-man]

Hi friends,
I've seen in many movies the windows of a car exploding after someone has had a great fall and landed on the car. Would anyone care to explain to me why this happens?

 

[Cyrus]

Sure, because it makes for good tv. You can shoot a tank of propane and nothing will happen. In fact unless its a VERY powerful gun, it will just bounce off. If it is a powerful gun, it will just make a hole and leak out. Sorry, no explosions here either.

 

[Ki Man]

Sure, because it makes for good tv. You can shoot a tank of propane and nothing will happen. In fact unless its a VERY powerful gun, it will just bounce off. If it is a powerful gun, it will just make a hole and leak out. Sorry, no explosions here either.

I think he's just referring to the windows shattering.

In the case that he isn't, a car that explodes on impact wouldn't even be street legal. Besides, who the h*** would be crazy enough to drive an exploding deathtrap anyways. There are all sorts of crazy things in films, like cars hitting poles at 60mph and bursting into flames. Maybe there would be an engine fire, but no automaker in their right minds would sell a car that unsafe (at least not here where its regulated, maybe in China..)

 

[FredGarvin]

The windows on vehicles are tempered or laminated safety glass. I believe the automakers are now using the laminated kind which has a thin layer of plastic in between two glass layers. That is why, if you have ever seen a real accident, the windows look like they can get peeled back from the car. They are meant to break into very small pieces with an impact, but they should not explode. The small pieces help to ensure that, in an accident, there are no large sharp protrusions that someone can get impaled on.

Windows exploding are, at best, a throw back to when there was simple plain glass in vehicles. They definitely do not work like that any longer.

Here's a link to How Stuff Works' site on the subject:
http://auto.howstuffworks.com/question508.htm

 

[capnahab]

One thing everybody is forgettin is that windows in a automobile do not explode but crack, mandated by the "holier than thou" US government. It is a cheap Hollywood trick.

 

[Danger]

While I've never seen car windows explode, I sure as hell have seen a few that imploded. Windshield safety glass is a bit of a joke in that regard. I once got called to make a set of keys for an impounded car that had been in a front-end collision. The entire front seat was plastered with little square bits of glass that looked fairly harmless... until I accidentally brushed my hand against one and ended up bleeding like a stuck pig for half an hour. (That was a mid-70's model; maybe things have changed.)

 

[nacho-man]

sorry friends i used the wrong word, i meant why do they shatter?

 

[FredGarvin]

The tempering process used in glass manufacturing sets up residual stresses in the glass. This is what forces the glass to shatter into very small pieces.

http://en.wikipedia.org/wiki/Toughened_glass