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Homework Help: Finding the force up an incline given horizontal force

  1. Jun 7, 2012 #1
    1. The problem statement, all variables and given/known data
    I need help with part of a problem. I am having problems understanding just how to find the force up an incline when a horizontal force ("headwind") is given.

    2. Relevant equations

    3. The attempt at a solution
    When drawing a triangle to figure it out I draw the hypotenuse as x (force I need to find) and the side adjacent to angle θ as Fapplied. From this, I get cosθ = Fapp/x, therefore x=Fapp/cosθ. However, my online homework listed it as Fapp*cosθ. Did I draw the triangle wrong?
  2. jcsd
  3. Jun 7, 2012 #2


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    Welcome to PF!

    Hi OneObstacle! Welcome to PF! :smile:
    I don't understand which of x and Fapp is the force to be applied, and which is the wind. :confused:

    (I also don't understand how you can have a horizontal headwind if you're facing up an incline. :redface:)
  4. Jun 7, 2012 #3
    The original problem is a skier heading down an incline (sorry, confusing wording). Fapp is the headwind heading into the slope, and Force x is what I randomly assigned the force of the wind acting on the skier.
  5. Jun 8, 2012 #4


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    Hi OneObstacle! :smile:

    (just got up :zzz:)
    ohh! … you mean Fx is the component of the wind force in the x direction (ie up the slope)?

    ok, then your book is correct …

    don't start drawing triangles, just use this rule:

    to find the component of a (complete) force, we always multiply by cos of the angle between

    Fx = Fappcosθ :smile:
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