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Homework Help: Direction of angular acceleration

  1. Feb 6, 2008 #1
    1. The problem statement, all variables and given/known data
    Imagine a car driving on the XY plane in the +y-direction. If it is slowing down, in what direction is the angular acceleration of the wheels?

    (a) the +x-direction
    (b) the -x-direction
    (c) the +y-direction
    (d) the -y-direction
    (e) the +z-direction

    2. Relevant equations
    a=αR


    3. The attempt at a solution
    I am just really lost when it comes to this problem. The apparent answer is A, but I do not understand why. I can't conceptualize angular acceleration with the axes..

    The solution says the wheels have an angular velocity in the -x-direction and thus since the angular velocity is decreased the acceleration would be in the +x-direction. I get the second step, but I don't understand how you determine the angular velocity is in the -x-direction
     
    Last edited: Feb 6, 2008
  2. jcsd
  3. Feb 6, 2008 #2
    Actually, I think I get it now after messing around with some pictures..still, I think this was a stupid and poorly phrased problem.
     
  4. Feb 7, 2008 #3
    think it as applying a force to stop the wheels....
     
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