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Homework Help: When a bird flies into a bar; solving for angular velocity

  1. Apr 10, 2013 #1
    1. The problem statement, all variables and given/known data

    A 550.0g bird is flying horizontally at 2.20m/s , not paying much attention, when it suddenly flies into a stationary vertical bar, hitting it 25.0cm below the top. The bar is uniform, 0.730m long, has a mass of 2.20kg , and is hinged at its base. The collision stuns the bird so that it just drops to the ground afterward (but soon recovers to fly happily away).

    0.55 kg = mass of bird
    2.2 m/s = velocity of bird
    0.48 m = distance from axis of rotation bird hits bar
    0.73 m = length of bar
    2.2 kg = mass of bar

    A)What is the angular velocity of the bar just after it is hit by the bird?

    B)What is the angular velocity of the bar just as it reaches the ground?

    2. Relevant equations

    KE(bird) = (1/2)mv2
    KE(bar) = (1/2)Iω2
    I(bar) = (1/3)mr2

    3. The attempt at a solution

    (1/2)mv2 = (1/6)mr2ω2
    ω = 2.75

    For part B I can't solve until I have the answer to part A
  2. jcsd
  3. Apr 10, 2013 #2
    I found my mistake for part A.

    The answer to part A is 1.486
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