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Homework Help: Conservation of Energy problem.

  1. Nov 23, 2009 #1
    1. The problem statement, all variables and given/known data
    A 0.030-kg bullet is fired vertically at 200 m/s into a 0.15-kg baseball that is initially at rest. How high does the combined bullet and baseball rise after the collision, assuming the bullet embeds itself in the ball?

    2. Relevant equations
    m1v1 + m2v2 = (m1 + m2) v'

    3. The attempt at a solution

    0.030 kg * 200 m/s + 0.15 kg * 0 m/s = (0.030 kg + 0.15 kg) v' = 6 = 0.18 v'
    v' = 33.333 m/s
    [tex]\Delta[/tex]p = m(vf-vo) = 0.18 kg (33.333 m/s) = 5.999 = 6 kg * m/s

    Ok, this is what I did so far. Even though I know the velocity of the bullet + ball, I don't know how high it went up because I think I need to know the time or acceleration to find x, which is height.

    Please help me what to do next.
  2. jcsd
  3. Nov 23, 2009 #2


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    Homework Helper

    The acceleration is -9.81 m/s².
  4. Nov 24, 2009 #3
    but I don't know the time.
  5. Nov 25, 2009 #4


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    Staff Emeritus
    Science Advisor
    Homework Helper

    Take a look at the kinematic equations for constant acceleration. One of them will work here.
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