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Homework Help: Vectors are parallel

  1. Sep 7, 2011 #1
    1. The problem statement, all variables and given/known data
    Given vectors b and c are they parallel? If so find such scalar s that c=sb, otherwise write N for no.

    a) b=<0,3,4>, c=<0,6,-8)

    b) b=<10,6>, c=<-15,-9>

    2. Relevant equations

    c=sb is a property of the dot product.

    3. The attempt at a solution
    For a) I put No because <0,6,-8> does not = <0s, 3s, 4s> because S=2
    For b) I put Yes because S=-3/2 which would give you both outcomes of the vectors

    Am I correct?
  2. jcsd
  3. Sep 7, 2011 #2


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    Yes, you are. If you'd explain why you need to pick s=2 in the first case, that would probably help. "because s=2" isn't much of an explanation.
  4. Sep 7, 2011 #3
    I put s=2 because I was finding a multiple of the two vectors given. Then I calculate 3s=6, that would then calculate to c=2.
  5. Sep 7, 2011 #4


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    Right, so the only possibility is s=2, and since that doesn't work there is no s that works. I knew you knew that. Just wanted you to add that if you are turning this in as a homework exercise.
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