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Homework Help: Speed & Direction of Motion

  1. Apr 28, 2013 #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 600g falcon flying at 20.0m/s hit a 1.40kg raven flying at 8.0m/s. The falcon hit the raven at right angles to its original path and bounced back at 5.0m/s. By what angle did the falcon change the raven's direction of motion? What was the raven's speed right after the collision?

    2. Relevant equations
    ΔP, arctan(P_y/P_x)

    3. The attempt at a solution
    I tried to find each individual momentum vector for the raven and falcon, then did arctan(P_fal/P_rav) to get the direction of the motion, but my answer of 47° turned out to be incorrect. Could someone please guide me on how to work out both of these problems?
  2. jcsd
  3. Apr 28, 2013 #2


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    Remember, the momentum of the falcon is not going to come into play when finding the direction of motion of the raven. Why don't we find the x and y components of the raven's final momentum and go from there?
  4. Apr 28, 2013 #3


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    That doesn't compute the direction of anything interesting as far as I can see.
    Please post all your working:
    - the momentum vectors for the two birds before collision
    - the conservation of momentum equations
    - the raven's velocity vector after collision
    (Btw, the problem composer is clearly no ornithologist!)
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