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Homework Help: Resultant vector

  1. Jan 22, 2015 #1
    1. The problem statement, all variables and given/known data
    Three vectors A, B, C have magnitudes A=5, B=6 and C=7.
    The minimum value of |A+B+C| is
    *A represents magnitude, A represents the vector (magnitude and direction)
    2. Relevant equations

    3. The attempt at a solution
    I got 4 because I think that the maximum possible cancellation occurring would be 7-(6+5). But it's wrong.
  2. jcsd
  3. Jan 22, 2015 #2


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    Gold Member

    Im not sure exactly how to approach this, i have a guess, but ill have to work on it. Im off to bed now, though. An example. Let the magnitude 6 vector point at 120 degrees. Let the 5 magnitude vector point at 60 degrees. Let the 7 vector point directly down. Whats the magnitude? Can you mathematically find a relationship between the vector components and their magnitudes?
  4. Jan 22, 2015 #3
    I just figured it out, but thanks anyway. The three vectors can form the sides of a triangle, so the minimum will be zero.
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