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Homework Help: Uniform circular acceleration and direction

  1. Sep 19, 2008 #1
    1. The problem statement, all variables and given/known data
    Birds of prey rise up and down on thermals. A bird completes circle of radius 8m every 5s and rises vertically at a rate of 3.0 m/s. Assume uniform acceleration. Find

    a)speed of bird relative to ground
    b)magnitude of acceleration
    c)direction of birds acceleration
    d)angle between birds velocity vector and horizontal.


    2. Relevant equations
    ar=V^2/R


    3. The attempt at a solution

    I have found the answer to a be 10.5 m/s, the answer to b is 12.6 m/s^2

    c)at/ar=tan^-1(3/12.6)=13.3 degrees

    d) I'm not sure how to proceed for this equation.

    Any help is greatly appreciated and thank you for your time.
     
  2. jcsd
  3. Sep 19, 2008 #2

    Kurdt

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    For part c the bird is in uniform circular motion. The bird is rising at a rate of 3m/s is not an acceleration.

    For part d you have the vertical component of velocity and the component tangent to the circular motion. Find the resultant.
     
  4. Sep 19, 2008 #3
    Thanl you very much sir for the help and I finally got d :). HOwever I'm still a little bit confused about c. Centripetal acceleration has the same magnitude but varying direction so how am I supposed to find the direction of the birds acceleration above the horizontal.
     
  5. Sep 19, 2008 #4

    Kurdt

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    C says nothing about direction above the horizontal, it merely asks for direction as you have typed it.
     
  6. Sep 19, 2008 #5
    I see, thanks again.
     
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