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Homework Help: Calculate resultants of two forces

  1. Jan 27, 2013 #1
    1. The problem statement, all variables and given/known data

    Where does the resultant of the two forces act?


    2. Relevant equations

    None really. Basic algebra for calculating resultants.

    3. The attempt at a solution

    First off, I have tried to calculate the x and y components of the resultant, call it R. Here I think that R_{x}=0 (both forces are vertical) and R_{y}=-20 (net force in the y-direction). So the resultant is:

    R=R_{x}+R_(y} = 0x-20y with magnitude of 20N. However, I am unable to understand how the lengths will help me.
    Last edited: Jan 27, 2013
  2. jcsd
  3. Jan 27, 2013 #2

    Simon Bridge

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    The question wants you to replace the two forces at different distances with one force that has the same effect. So - what is the effect of each force as drawn? (Hint: what is special about point A?)
  4. Jan 27, 2013 #3
    That is what I have tried to do actually. I have replaced them with one downward force with magnitude 20N. But I don't know where it is located.

    What is special about point A? Well, not sure. There must be a force to compensate the downward force but that is done by the beam(object).
  5. Jan 27, 2013 #4

    Simon Bridge

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    20N is what you'd get if the forces acted along the same line.
    Do they?

    Won't each of the two forces create a moment about point A?
  6. Jan 27, 2013 #5
    Yes, I suppose. I will have to think a little bit about this one before I answer. Not sure about the theory yet.
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