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Homework Help: Impulse on a Cannon Ball

  1. Aug 27, 2011 #1
    1. The problem statement, all variables and given/known data

    The impulse on a human cannon ball is 2.5  103 N·s. The cannon
    ball has a mass of 65 kg.

    2. Relevant equations

    How long is the barrel of the cannon if the cannon ball leaves the
    cannon at 120 km/h?

    3. The attempt at a solution

    I used the formula J=ma(delta t)
    (2.5x 10^3)=(65)(a)(0.2)

    to find the acceleration. Then, I used the formula d=v1(t)+(1/2)(a)(t^2) to find the distance, and I got 3.85 m, but the answer at the back is wrong.

    Can anybody help me?
     
  2. jcsd
  3. Aug 27, 2011 #2
    How did you get the time of 0.2 seconds ?
     
  4. Aug 27, 2011 #3
    That's given in part a of the question, which I already got. Here's the entire question:

    The impulse on a human cannon ball is 2.5  103 N·s. The cannon
    ball has a mass of 65 kg.
    a) What force does the cannon exert on the human cannon ball if
    it takes 0.2 s for the human cannon ball to leave the cannon?
    b) How long is the barrel of the cannon if the cannon ball leaves the
    cannon at 120 km/h?
     
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