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Laws of Motion on a snow sled

  1. May 5, 2009 #1
    1. The problem statement, all variables and given/known data
    A person on a snow sled(total mass of 60.0kg) starts from rest at a vertical height of 24.0m above the bottem of the hill. If aconstant frictional force of 70.0 N opposes their motion as they slide down the hill and the length of the slope is 65.0m, whta is their speedat the bottem of teh hill?


    2. Relevant equations
    PE = KE + W
    mgh = 1/2mv2 + 1/2kx2


    3. The attempt at a solution
    (60kg)(9.8m/s2)(24m) = 1/2(60kg)v2 + 1/2(70N)(65m)2

    14112 = 30v2 +147875

    v=66.77m/s ??
     
  2. jcsd
  3. May 5, 2009 #2
    1/2kx^2? That's the equation for a spring, not for the energy lost due to friction.

    Just check your dimensional analysis, your units don't make sense.
     
  4. May 5, 2009 #3
    Recall the equation for Work Done...
     
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