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Finding distance of a block with an unattached spring

  1. Jul 5, 2013 #1
    1. A 9 kg block is pushed by an external force against a spring with spring constant 118 N/m until the spring is compressed by 2.1 m from its uncompressed length (x= 0). The block rests on a horizontal plane that has a coefficient of kinetic friction of 0.67 but is NOT attached to the spring. After all the external forces are removed (so the compressed spring releases the mass) how far D along the plane will the block move before coming to a stop? The acceleration due to gravity is 9.8 m/s^2.



    2. Relevant equations
    U=1/2kx^2
    KE= 1/2mv^2


    3. The attempt at a solution

    If i'm not mistaken, I have to use one of the acceleration formulas,but first i have to find the velocity of the block with the kinetic energy formula
     
  2. jcsd
  3. Jul 5, 2013 #2

    Doc Al

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    Staff: Mentor

    I suggest using energy methods to solve this.
     
  4. Jul 5, 2013 #3
    so, i just use KE and U? and how will it be then?
     
  5. Jul 5, 2013 #4

    Doc Al

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    Staff: Mentor

    Don't forget the work done against friction.
     
  6. Jul 5, 2013 #5
    so then it will be, KE+U-W=Total Energy ?
     
  7. Jul 5, 2013 #6

    Doc Al

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    Staff: Mentor

    I'd put it this way. At any moment, the total mechanical energy = KE + U. The change in the total mechanical energy will equal the work done by friction.
     
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