B2 High-Intermediate UK 20906 Folder Collection
After playing the video, you can click or select the word to look it up in the dictionary.
Loading...
Report Subtitle Errors
We’re at one of the UK’s leading firework manufacturers
and this is their 125 mm air starburst shell.
A 20-minute display will not drop 10,000 fireworks.
And 60% of them will release bad boys.
Each one costs around £ 30 and contains half a kilo of explosive.
And we have to launch it to a height to over 100 meters.
As you can see, it’s much more than a bowl of loose powder.
And this is how they test the component parts.
The basic firework recipe is flash powder,
a potent form of gunpowder.
It’s a mixture of Potassium Perchlorate and Aluminium.
These ingredients are mixed together in 7 kilo batches
and a small sample is ignited to make sure it has a requisite brightness.
This sample has been mixed with Strontium to make it glow red and it’s clearly a pass.
Well, this sample has Barium added to glow green.
Again, it does the trick nicely.
If a firework is packed with this loose powder,
it would explode in one instant flash.
So the gun powder mixture is turned into pellet to prolong the burn time.
As the burning pellets go to the sky,
they create the spreading patterns we are all familiar with.
This test checks whether this particular pellets size will burn of its efficient time
to create a burst diameter of 18 meters.
There are two roughly formed rings of stars – central ring and an outer ring.
The outer ring is made of stars of a slightly larger size.
Therefore their behaviour and when they burst in the middle
ignites these stars and blows them in the circle formation.
The initial will be the heavy larger stars will travel further.
That’s in the sky you’ll see one small ring and then a larger ring around it.
The next test checks the fireworks 2 fuses.
Firstly, a length of fuse is measured down to which it’ll slowly burn inside the firework
to ensure it ignites at the correct altitude.
A fuse this length should burn any about 12 seconds.
It has, so it’s a pass.
As second external fuse is needed to lose the firework.
Racking the fuse in paper should contain the hot gases
and make the fuse burn much quicker.
We expect this link to fuse to burn within a hundred fifty second.
Looks like a pass to me.
The final test is to ensure the firework is no louder than European regulation of 120 decibels.
The same noise level as enigmatic drill at close range.
    You must  Log in  to get the function.
Tip: Click on the article or the word in the subtitle to get translation quickly!

Loading…

Loading…

I Didn't Know That - Fireworks

20906 Folder Collection
Go Tutor published on December 29, 2014
More Recommended Videos
  1. 1. Search word

    Select word on the caption to look it up in the dictionary!

  2. 2. Repeat single sentence

    Repeat the same sentence to enhance listening ability

  3. 3. Shortcut

    Shortcut!

  4. 4. Close caption

    Close the English caption

  5. 5. Embed

    Embed the video to your blog

  6. 6. Unfold

    Hide right panel

  1. Listening Quiz

    Listening Quiz!

  1. Click to open your notebook

  1. UrbanDictionary 俚語字典整合查詢。一般字典查詢不到你滿意的解譯,不妨使用「俚語字典」,或許會讓你有滿意的答案喔