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Homework Help: Kinetic Energy

  1. Oct 16, 2008 #1
    1. The problem statement, all variables and given/known data
    Find the total kinetic energy in the system. a explosion fires two pieces both 7.3m high and 11.2m horizontally total kinetic energy done by the explosion the first piece is 15kg, the second 26kg?

    2. Relevant equations

    3. The attempt at a solution
    I found that Vi(y) = [tex]\sqrt{2(9.81)(-7.3)}[/tex] = 11.96 m/s do i just use this to find the total energy done? or do i need to consider the x-dir as well, If so how do i do that?
  2. jcsd
  3. Oct 16, 2008 #2


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    Hi Grogerian!

    The KE depends on the total speed, as you know, so Vy is obviously not enough unless Vx is zero.

    (but I can't help any furher, as I don't understand the question. :redface:)
  4. Oct 16, 2008 #3


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    Velocity is the sum of the components, so yes, you do need to determine the x component.

    Since you can figure the time to drop 7.3m from the peak and you know that will be half the time of its flight, and you know that is 7.3m = 1/2 g*t2. Now you can figure how fast it was to go 11.3m.
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