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Homework Help: Three forces acting on a point

  1. Oct 12, 2008 #1
    I'm sorry that this is probably a repeat topic, but I am having a hard time using other threads as examples. This is probably really easy, I just can't seem to figure it out the way our teacher taught it. I'll try and make this short and simple.

    1. The problem statement, all variables and given/known data

    There are three forces acting on a single point. One is 15 N north; the second is 15 N west; and the final is 15 N at 30 degrees east of north. Determine the magnitude and direction of the resultant force.

    2. Relevant equations

    Basic trig (sin, cos, tan), a^2 + b^2 = c^2. This is all we have been taught in this class and are expected (and should be able to) solve with just this.

    3. The attempt at a solution

    PHP:
            10 N north
                |  /
                | /   15 N 30 degrees east of north
    <-----------|/    
       15 N west
    From there I am unsure of what I could do to easily solve it (also a little unsure of what I am even solving for).
     
    Last edited: Oct 12, 2008
  2. jcsd
  3. Oct 12, 2008 #2

    Doc Al

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    Staff: Mentor

    One easy way to add vectors is to find their components (x & y = East-West & North-South) and add them. Then you can find the magnitude and direction of the resultant from its components.
     
  4. Mar 9, 2011 #3
    Could you please help me with theory of vectors at equilibrium?
     
  5. Mar 9, 2011 #4

    Doc Al

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    Staff: Mentor

    If an object is in equilibrium, the forces acting on it (which are vectors) must add to zero. Is that what you mean?
     
  6. Mar 9, 2011 #5
    For the original poster: any question like this, even one with 2034 forces acting on a point, can easily be solved by breaking each vector into x and y components and then adding up to find the resultant. Some people find a chart helpful.

    V| x | y
    1| 0 | 10
    2|-15| 0
    3| ?x| ?y

    The total in the x direction would be -15 + ?, and the total in the y would be 10 + ?y.

    To find ?x and ?y will require some trig.
     
  7. Mar 9, 2011 #6

    Doc Al

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    Staff: Mentor

    Realize that this thread is about 2 1/2 years old.
     
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