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Homework Help: Bird Collision Problem

  1. Jun 26, 2010 #1
    1. The problem statement, all variables and given/known data

    To protect their young in the nest, peregrine falcons will fly into birds of prey (such as ravens) at high speed. In one such episode, a 620 g falcon flying at 20.0 m/s hit a 1.40 kg raven flying at 9.0 m/s. The falcon hit the raven at right angles to its original path and bounced back at 5.0 m/s. (These figures were estimated by the author as he watched this attack occur in northern New Mexico.)

    A.By what angle did the falcon change the raven's direction of motion?
    B.What was the raven's speed right after the collision?

    2. Relevant equations

    conservation of momentum

    3. The attempt at a solution

    I put the falcon on the y axis and the raven on the x axis, I ten tried to find the a and y components of p then did theta= arctan9p2/p1) which gave me 45 degrees-wrong

    I then tried to find the x and y components using
    m_F_v_Fi + m_R_V_Ri = m_F_v_Ff + m_R_V_Rf

    Solving for v_Rf for the x and y compents I got 9 and 8.16 respectively, the had theta= arctan(8.16/9)= 42 degrees again wrong.
  2. jcsd
  3. Jun 26, 2010 #2


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    Science Advisor

    Precisely how did you get that? Are you assuming a perfectly elastic collision? That's probably not correct. What percentage inelasticity are you assuming?

  4. Jun 26, 2010 #3
    Pretty much I did p=sqrt(p_1_^2 +p_2_^2

    But I realize that is wrong because its not elastic situation, I know is inelastic, but not perfectly inelastic so I used the second equation thinking that would work, I'm not quite sure were to go from there.
  5. Jun 26, 2010 #4
    Never mind I was doing it correctly, I just kept making some unknown calculation error that kept giving me the wrong angle.
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