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Finding Net Force [w/ Vector Addition]

  1. Oct 24, 2013 #1
    1. The problem statement, all variables and given/known data

    A 20 kg object is being acted on by a 90 N [E60N] force, a 40 N force, and a 40 N [E27S] force.
    Find the net force acting on the object and its acceleration.

    2. Relevant equations

    ƩF = ma

    3. The attempt at a solution

    I understand that I have to add vector components here.
    So as a result, I got 80.64 N [E] and 19.78 N [N].
    I got a force pulling North and a force pushing East. But now I don't know what to do with these forces...?
  2. jcsd
  3. Oct 24, 2013 #2
    Assuming you worked correctly so far, these are the components of the resultant force.
    You need to find the magnitude and the direction (angle) of this resultant.
  4. Oct 24, 2013 #3


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    Well, what force vector did you get when you added the components of the original three vectors which were given? Don't you get a Resultant vector with a magnitude and a direction?

    Can't you use this resultant vector to answer the second part of your problem?
  5. Oct 24, 2013 #4
    Oh, so is it right for me to use Pythagorean theorem here to find the resultant vector?
    and then that would be the net force which can be used to determine acceleration, correct?

    *I worked it out and got 83.03 N [E3.5N]
    Just wondering if it's necessary to include direction [E3.5N]
    I know acceleration is a vector quantity but what does this implicate? Simply the direction of acceleration for my final answer?
  6. Oct 25, 2013 #5


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    Yes, the direction of the acceleration is always in the direction of the net force.
  7. Oct 25, 2013 #6
    Ok, thank you!!
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