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Homework Help: Work Energy principle

  1. Mar 15, 2015 #1
    1. The problem statement, all variables and given/known data
    An object is traveling at 10m/s. along an inclined surface of an angle 10°. How far does it go up the bank?
    How fast will it be going when it travels back down?
    Coefficient of friction is .15

    2. Relevant equations
    Ei = Ef
    Ef - Ei = Eloss

    W = Fd

    3. The attempt at a solution
    I dont really know where to start. I made a FBD.
    ∑Fx = gsinθ+ukgcosθ = ma
    There are two unknowns. I dont know the distance. and I dont know how much energy is lost in the displacement.

    If there was no friction I could solve it using Ei = Ef but with friction I dont know where tostart. Can anyone tell me the first step?
  2. jcsd
  3. Mar 15, 2015 #2
    I tried again. 1/2mv^2 = ukmg cos∅d+mgh
    h = d sin∅
    (v^2)/(2g(cos∅+sin∅)) = d =32.6 m
    That is the displacement. I think.
    use h = dsin∅ to find initial H
    use mgh = ukmgcos∅d+1/2mv^2 to find v
    Is that correct?
  4. Mar 15, 2015 #3


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    (Use X2 icon for superscript, X2 for subscript.)
    That's a good start.

    It looks like you left μk out of the following equation.
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