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Three vectors A, B, and C add together to yield zero

  1. Oct 21, 2009 #1
    1. The problem statement, all variables and given/known data

    Three vectors A, B, and C add together to yield zero: A + B + C = 0. The vectors A and C point in opposite directions and their magnitudes are related by the expression: A = 2C. Which one of the following conclusions is correct.

    A. B and C have equal magnitudes and point in the same direction.
    B. A and B have equal magnitudes and point in opposite directions.
    C. B and C have equal magnitudes and point in opposite directions.
    D. A and B point in the same direction, but A has twice the magnitude of B.
    E. B and C point in the same direction, but C has twice the magnitude of B.


    2. Relevant equations

    A + B + C = 0

    A = 2C

    3. The attempt at a solution

    I've never been good at these types of problems. They feel like brain teasers. I was thinking about replacing A, B, and C with numbers. A being equal to 2 times C. But that didn't work out as smoothly as I had hoped.

    Um...help, please?
     
  2. jcsd
  3. Oct 21, 2009 #2
    A points in the opposite direction of C, so there is a negative involved: A = -2C.
    With this, you can view it as
    -2C + B + C = 0 ... (1)
    -C + B = B - C = 0 ... (2)
    Now you just have to figure out what set of vectors for B satisfy expression (2).
     
  4. Oct 22, 2009 #3
    Sorry, I'm still not following...

    Expression (1) makes sense, but (2) doesn't...
     
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