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Homework Help: Conservation of Energy problem!

  1. Jan 16, 2013 #1
    1. The problem statement, all variables and given/known data

    Here's the problem :

    http://www.diigo.com/item/image/2sb3i/wonu [Broken]

    2. Relevant equations

    Ei = Ef

    3. The attempt at a solution

    The surface between A and B is frictionless :
    Ei = Ef
    KA + UA = KB + UB
    mghA = 1/2 mvB2
    vB2 = 2ghA = 2*9.8*3 = 58.8 m/s

    The surface from C to the spring is frictionless :
    Ei = Ef
    1/2 mvC2 = 1/2 kx2
    vC2 = kx2/m = 2250*0.32/10 = 20.25 m/s

    The surface between B and C has a friction :
    Ef - Ei = -fkd
    1/2 mvC2 - 1/2 mvB2 = -ukmgd
    1/2 m (vC2 - vB2) = -ukmgd
    1/2 * 10 (20.25 - 58.8) = -uk*10*9.8*6
    uk = 0.327

    Right?
     
    Last edited by a moderator: May 6, 2017
  2. jcsd
  3. Jan 16, 2013 #2
    I haven't double checked each computation, but your method is correct and the final answer is reasonable.
     
  4. Jan 16, 2013 #3
    LastOneStanding, Thank you.
     
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