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Homework Help: Newtonian Force Problem

  1. Oct 11, 2009 #1
    1. The problem statement, all variables and given/known data
    Two forces act on an object of mass 2.5kg; force F1 that is directed alont the +x-direction and has magnitude of .50N and force F2 that points at a 45 degree angle in the +y and -x quadrant and has magnitude 2.0N. Find the additional force, if any such that the object will accelerate in the +y direction with magnitude 1.5m/s/s.

    2. Relevant equations

    3. The attempt at a solution
    Fnety= F2sin[tex]\theta[/tex]+FX-Fg

    FX= missing force= ?
    Fnety= (2.5kg)(1.5m/s/s)= 3.75N
    F2sin[tex]\theta[/tex]= 1.414N
    Fg= 2.5*9.8=24.5N

    3.75 = FX + 1.414 -24.5
    FX= 26.84N

    I'm not sure if I'm even trying to go about the problem correctly.

    The selected answers in the back of the book has the answer as:

    so I'm really confused.
  2. jcsd
  3. Oct 12, 2009 #2


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    Homework Helper

    Let the third force be xi + yj.
    Take x and y components of all the three forces. Since the resultant force is along y axis, total x-component must be zero.
    Hence total y component must be equal to .....?
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