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Homework Help: Simple Vector Problem. Help please!

  1. Oct 12, 2005 #1
    Hey everyone,
    I know this problem is easy but im having some trouble. If someone could point me in the right direction i would be really grateful.
    Suppose (vector)C=(vector)A + (vector)B
    a) under what circumstances does [A]=+[C]?
    b) Could [C]=[A]-?
    ( [ ]= absolute value)
    Ok. For A i think that A and B would have to have the same signs but Im really not to sure.
    For B i cant see how C=A+B can be equal to [C]=[A]-. It seems like a simple contradiction, which usually means im wrong. :tongue2:
    I would really apprecitate some help!!!!
  2. jcsd
  3. Oct 12, 2005 #2
    Try drawing any two random vectors A and B on a piece of paper. Then draw vector C = A + B. Is it possible for you to draw A and B such that the lengh of A plus the length of B is equal to the length of C?
  4. Oct 12, 2005 #3


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    Homework Helper

    Antiflag - for (a), did you mean |C| = |A| + |B|? That's the question Tzar hinted at.

    For (b), you were on the right track with your other answer. Think: the difference between vector addition and scalar addition is that vectors have direction. Does the - sign have any meaning with respect to direction?
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