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Homework Help: Slinging mass

  1. Jul 27, 2015 #1
    1. The problem statement, all variables and given/known data
    There is a wagon (W) on wheels with a vertical pole of 2m. (mass 20kg)
    On the top of that pole there is a rope pendulum with an attached mass (M) of 10kg and length 1m.
    The starting position is a pendulum angle of 60°.

    No friction taken into account.
    What is the speed of the mass compared to the wagon the first time it passes the pole?

    2. Relevant equations
    Ep= m * g * h
    Ek= m*v²/2

    3. The attempt at a solution
    EM0= 10kg * 10 m/s² * (1m *cos60) = 50J
    EW0= 0
    EM1= 10kg*VM²/2
    EW1= (10kg+20kg) *VW²/2


    And now i don't know how to continue.
  2. jcsd
  3. Jul 27, 2015 #2
    Conservation of linear momentum?
  4. Jul 27, 2015 #3
    Ok, thanks!
    I made an error by summing the masses for EW1.
    Solution is 3.87m/s for the interested.
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