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-Unsolved-Work, Energy problem and friction

  1. Oct 9, 2011 #1
    ----Unsolved----Work, Energy problem and friction

    EEEK I already posted this problem, but I cannot find it anymore! SO here it is again!

    A student, starting from rest, slides down a water slide. On the way down, a kinetic frictional force (a nonconservative force) acts on her. The student has a mass of 70 kg, and the height of the water slide is 11.3 m. If the kinetic frictional force does -7.6 × 10^3 J of work, how fast is the student going at the bottom of the slide?

    Vo = 0 m/s
    m = 70 kg
    Ho = 11.3 m
    Hf = 0 m
    Wnc = -7.6 x 103 J

    Wnc = 0.5m(Vf2 -Vo2) + mg(Hf-Ho)

    -7.6 x 103 = 0.5(70)(Vf2) + 70(9.8)(11.3)

    Vf = 20.9 m/s

    A person on physicsforum tried to help me but it was the wrong answer, and I only have one chance left to answer it correctly on the computer software. please help?
     
  2. jcsd
  3. Oct 9, 2011 #2

    Doc Al

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    Staff: Mentor

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