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Work-energy theorem.

  1. Mar 26, 2013 #1
    10kg block is pulled up an incline plane at 30 degree with horizontal in distance 5.0m by force 120N.coefficient of kinetic energy 0.4.

    help!how do you get the velocity of block? answer: v=3.48ms^-1
     
  2. jcsd
  3. Mar 26, 2013 #2

    rude man

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    Are you looking for the velocity at 5m with velocity = 0 at 0m? Or what?
     
  4. Mar 27, 2013 #3
    the velocity of the block after it has move 5m up the plane
     
  5. Mar 27, 2013 #4

    Doc Al

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    I assume you meant that the coefficient of kinetic friction is 0.4.

    So what does the work-energy theorem say? What forces are acting on the block? How much work do they do?
     
  6. Mar 27, 2013 #5
    *correction- kinetic friction*.
    frictional force,the gravitational force,applied force and normal force.The work done by gravitational force=-245.25J,energy lost by overcoming friction=-169.92J,work done by force,120N=600J, and the total work done i found was 184.83J. so how do I get the velocity of the block after it has move 5m up the plane?
     
    Last edited: Mar 27, 2013
  7. Mar 27, 2013 #6

    Doc Al

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    Assuming you've calculated the total work correctly, use the work-energy theorem! Total Work = ΔKE.
     
  8. Mar 27, 2013 #7

    Doc Al

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    I don't see how you can get that answer from the given data.

    Is the applied force parallel to the incline?

    If this from a textbook, tell me which book and problem.
     
  9. Mar 27, 2013 #8
    applied force is parallel.
    and no its not from txtbook
     
    Last edited: Mar 27, 2013
  10. Mar 27, 2013 #9

    rude man

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    work in = friction loss + gain in potential energy + gain in kinetic energy.

    You are very close to solving this problem. Your numbers agree with mine. So where do the 185 J go at the top of the ramp?

    BTW I believe the given answer is wrong if v = 0 at the bottom of the ramp.
     
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