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Homework Help: Vectors and Forces

  1. Jun 22, 2010 #1
    1. The problem statement, all variables and given/known data

    If θ=30 degrees find the direction and magnitude of the resultant of these forces.
    [PLAIN]http://img194.imageshack.us/img194/7899/image2iw.jpg [Broken]

    2. Relevant equations



    3. The attempt at a solution

    Ok, so I know I have to add both of the vectors. I need to find the coordinates to do so. The first vector's coordinates must be <220,0>. Next I need to find the second vector's coordinates:

    x=150cos30
    x=[150√(3)]/2
    y=150cos30
    y=75

    so the second vector has the coordinates <[150√(3)]/2,75>

    If you add the second and the first vectors you get <[590√(3)]/2,75>

    Then I found the magnitude of this new vector to be 590.63 newtons. However, this is wrong because the book's answer section says the magnitude should be 357.85 newtons.

    If i go on to find the direction that also turns out wrong. What am I doing wrong?
     
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Jun 22, 2010 #2

    Mark44

    Staff: Mentor

    The x-component of your vector sum is 590*sqrt(3)/2, which is about 510. That is incorrect, and is too large (you should get about 350). Take a look again at your calculation for this component.
     
  4. Jun 22, 2010 #3
    Ahh. Thanks, I found my error. The x component should be:

    [440+150√(3)]/2
     
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