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Firecracker physics

  1. Jul 5, 2010 #1
    Hello, this question may not be appropriate for this forum, but I feel that chemistry people are more likely to understand the basic operational characteristics of firecrackers.

    Say I have a standard obnoxious firecracker, like the ones that they sell connected in strings for your neighbors to detonate early in the morning. The firecracker is just a bunch of black powder in a cardboard tube, and the tube explodes when the fire reaches it.

    My question is how the tube explodes. Is the explosion somewhat omnidirectional, or does it favor the poles of the cardboard tube? By that I mean, if I were trying to pry open a door or something (not that I am, this is just to illustrate), would more force be directed onto the two surfaces if the firecracker was inserted lengthwise or on its end?
     
  2. jcsd
  3. Jul 6, 2010 #2
    Lengthwise.

    Look up shaped charges. Firecrackers aren't that sophisticated but it's still interesting.

    Don't try to make one. You get a horrible injury to yourself or someone else. It's not fun.
     
  4. Jul 6, 2010 #3
    I assure you that I'm not planning on it :P

    So by lengthwise you mean with its ends touching the two surfaces? As in, more explosive force comes out of the poles of the cylinder? That makes sense to me, because that's the way the expanding gases are more likely to go, but I thought I should check. Thank you very much.
     
  5. Jul 16, 2010 #4
    if you look up at a blown up firecracker (the "blackjack"/on a string type) you will find they split at the middle, leaving the two ends more or less intact

    so i dont think you would get more mileage out of one by directing one of its poles at your target
     
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