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Conservation of Energy block of mass

  1. Oct 23, 2006 #1
    A small block of mass m1 = 0.600 kg is released from rest at the top of a curved wedge of mass m2 = 4.50 kg, which sits on a frictionless horizontal surface as in Figure P6.59a. When the block leaves the wedge, its velocity is measured to be 4.00 m/s to the right, as in Figure P6.59b.

    [​IMG]

    What is the height h of the wedge?

    Isn't this problem just conservation of energy
    I did
    KE+PE initial = KE + PE final
    0 + mgh = 1/2 mv^2 + 0 and solve for h v is 4.0 m/s
    9.8 h = 8
    h= .82
    but it saids i am wrong, plz help
     
  2. jcsd
  3. Oct 23, 2006 #2

    OlderDan

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    It is not just conservation of energy, and you have not accounted for all of the energy. The wedge is not stationary in this problem. What is conserved?
     
  4. Oct 23, 2006 #3
    oh i understand now, i have to include the kinetic energy of the wedge in the formula, thank you
     
  5. Oct 23, 2006 #4

    OlderDan

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    And you have to include another conservation principle
     
  6. Oct 23, 2006 #5
    oh ok, i got the answer now, thank you
     
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