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Homework Help: Body Diagram

  1. Mar 14, 2013 #1
    1. The problem statement, all variables and given/known data

    Two horses pull horizontally on ropes attached to a stump. The two forces F1= 1300 N and F2 that they apply to the stump are such that the net (resultant) force R has a magnitude equal to that of F1 and makes an angle of 90 with F1.

    What is the magnitude of F2?

    2. Relevant equations

    3. The attempt at a solution

    I got the answer correct but I was confused with the wording. F2 ended up being at some angle with respect to the x-axis and F1. I thought that this force was horizontal. Could somebody clarify this? Also could this be solved using the dot product?

    F2= 1838N
  2. jcsd
  3. Mar 14, 2013 #2

    Doc Al

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    Staff: Mentor

    When they say that the horses pulled horizontally, they just mean that the ropes were parallel to the ground, not angling upward or downward.

    If F1 is along the y-axis, then the resultant will be along the x-axis. You use that fact to solve for F2. (The x-y plane is the plane of the ground.)

    How did you solve it?
  4. Mar 14, 2013 #3



    F2sin(theta) =1300N


    F1+F2cos(theta) =ma


    -F1/cos(θ) =F2

    I substituted this into the Fy. I am not sure if this is the correct way to do it though.
  5. Mar 14, 2013 #4

    Doc Al

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    Staff: Mentor

    Please define your directions. Where is F1 pointing? What's θ?

    Instead of F = ma, just use ƩF = whatever. There's no acceleration involved, just adding forces.
  6. Mar 14, 2013 #5
    Yeah I did it over again with just forces. Thanks for your help.
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