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Homework Help: 3 Vectors Addition

  1. Jul 14, 2015 #1
    1. The problem statement, all variables and given/known data

    Three vectors, A, B and C each have a magnitude of 50 units. Their directions relative to the positive direction of the x-axis are 20°, 160° and 270°, respectively. Calculate the magnitude and direction of each of the following vectors.
    A+ →B+ →C
    A− →B+ →C
    2 ( →A+ →C)

    2. Relevant equations


    3. The attempt at a solution

    So I think i'm fine at figuring out the trig once I've set up the question/diagram of the vectors. Pictured above is my attempt as to what I assume the question is describing that the vectors are supposed to look like, but I am unsure about vector C which is 270 degrees. I feel like I might just be overlooking a minor detail foolishly but I am quite stuck! Does this look correct to anyone? Or does anyone interpret the question differently? Any help would be very much appreciated! Thank you in advance!
  2. jcsd
  3. Jul 14, 2015 #2
    Draw a better picture.

    Compute x and y components of each vector.

    Compute the desired sums and differences as x and y components.
  4. Jul 14, 2015 #3


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    Gold Member

    1) I am curious as to how you managed to get 20 + 120 to add up to 160.

    2) I think you are missing the point of drawing the vectors head to tail in the order specified by each part of the question.
  5. Jul 15, 2015 #4


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    Science Advisor
    Homework Helper
    Gold Member


    Better drawing required as your current one has errors. Read the problem statement again and use a protractor to plot the angles. Note that when drawing the problem statement all three vectors start at the origin. You might find there is some symmetry that can help simplify things later.

    Read up on the head to tail method to add the vectors and do separate drawings for each of a to c.
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