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Calculating the Work done from an Incline with Friction Problem

  1. Oct 12, 2013 #1
    Problem:
    A father pushes horizontally on his daughter's sled to move it up a snowy incline, as illustrated in the figure, with h = 3.6m and θ = 15°. The total mass of the sled and the girl is 35 kg and the coefficient of kinetic friction between the sled runners and the snow is 0.20. If the sled moves up the hill with a constant velocity, how much work is done by the father in moving it from the bottom to the top of the hill?

    wG8RI2Z.png

    Equations Used:

    Forcenet Y components ƩFy= N-mgcosθ=0-(due to constant velocity)
    So...
    Normal Force Fn= mgcosθ
    And since...
    Friction Force Ff= (μ)kFn
    So...
    Friction Force Ff= (μ)k(mgcosθ)

    Forcenet X components ƩFx= -mgsinθ-(μ)k(mgcosθ)

    3. The attempt at a solution

    Before I go any further with solving this problem I need to know how to use the applied Force from the father in this problem. I'm 100% certain my ƩFx is incorrect and was hoping someone could explain how I should fix this.
     
    Last edited: Oct 12, 2013
  2. jcsd
  3. Oct 13, 2013 #2
    Yes, ##ƩF_{x}## is incorrect because you calculated Normal force incorrectly. Since ##F## (force by father) is acting horizontally, you'll have to take component perpendicular to the plane into account while calculating ##ƩF_{y}##
     
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