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Ballistic bullet pendulum conservation of momentum problem

  1. Nov 8, 2013 #1
    1. The problem statement, all variables and given/known data
    A 15 g bullet is fired into a 2.55 kg block that is hanging by a 2.0 m long string. The speed of the bullet is 425 m/s.

    Calculate the angle when the system reaches its maximum height?


    2. Relevant equations
    m1v1=(m1+m2)vf

    (1/2)mv^2=mgh


    3. The attempt at a solution

    (0.015 kg)(425 m/s) = (0.015 kg + 2.55 kg)vf
    vf=2.49 m/s

    (.5)(2.565 kg)(2.49 m/s)^2=(2.565)(9.8)h
    h=.316 m

    Now that I have my height, I am not sure what to do. I think it should be a simple trig function at this point, but I cannot get the correct answer which is 32.6 degrees. I've also tried using L-Lcosθ=h, but have not had luck with that.

    Thanks in advance.
     
  2. jcsd
  3. Nov 8, 2013 #2

    ehild

    User Avatar
    Homework Helper
    Gold Member

    Your work is correct so far, and yes, use L-Lcosθ=h. What is your problem with it?


    ehild
     
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