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Homework Help: Simple problem about relative motion.

  1. Feb 7, 2013 #1
    1. The problem statement, all variables and given/known data
    A body consisting of two spheres attached by a 10 meter solid long rod is rolling down a 45 degree incline at one end while rolling up a 45 degree incline on the other end.
    At the instant when the connecting rod is horizontal the sphere rolling down has the velocity 2 m/s down the incline and the acceleration 3 m/s^2 down the incline. At this time, what is the velocity of the sphere rolling up and what is the angular velocity of the rod?

    2. Relevant equations

    VB = VA+ωXrB/A

    3. The attempt at a solution
    VB = VB*(cos(45)*ei+sin(45)*ej)
    rA/B= 10*ei
    Doing the calculations
    VB cos(45) = cos(45)
    VB*sin(45) = -2*sin(45)+10ω

    What am I doing wrong?
  2. jcsd
  3. Feb 7, 2013 #2


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    Gold Member

    I guess that's VB = vB*(cos(45)*ei+sin(45)*ej), to avoid the pun.
    ek, perhaps?
    What's ez? Do you mean ei?
    You've lost me - where did that come from?
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