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Firework Explosion

  1. Nov 5, 2009 #1
    1. The problem statement, all variables and given/known data
    During testing of a fireworks device an engineer records that data shown in the table below when the device, initially at rest, explodes under controlled conditions into three components that spread out horizontally. Determine the unknown quantity.
    http://img687.imageshack.us/img687/8969/screenshot20091105atnov.th.png [Broken]

    2. Relevant equations
    No idea how to attempt this at all.
    I am thinking that you use the momentum equation:
    m1v1 +m2v2 = m1v1' +m2v2'

    And potentially the kinetic energy equation (if it's elastic):
    0.5m1v1^2 +0.5m2v2^2 = 0.5m1v1'^2 +0.5m2v2'^2

    3. The attempt at a solution
    I have no idea where to start. If you could help that would be great.

    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Nov 5, 2009 #2


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    If it's an explosion then by definition momentum is conserved...

    parts 1 and 2 look like they're travelling north and east respectively so therefore in order to conserve momentum the 3rd part should travel southwest! So using the momentum of parts 1 and 2 as the opposite and adjacent parts of a triangle, you should be able to find the hypotenuse = momentum of part 3.

    Then p=mv, right, so you can find the velocity of part 3 from there!
  4. Nov 8, 2009 #3
    Now, would it be possible to solve this problem if they did not give the mass of the 3rd component (flying piece), if so, how?

  5. Nov 8, 2009 #4


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    If you use momentum p=mv to solve it, no, not unless they gave you the original mass of the device and then you just minused off the masses of the other parts to get your 3rd mass.

    Unless there's another way you can solve it?
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