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Homework Help: Dot Product confusion (no calculations involved)

  1. Jan 21, 2012 #1
    If I take the Dot Product of two vectors, say A and B, I get: AxBx + AyBy + AzBz

    And then when I add those terms, I get the magnitude, right?

    So when one of those terms are negative, that means I could end up with a negative magnitude?

    I thought magnitude had to be positive.
  2. jcsd
  3. Jan 21, 2012 #2

    I like Serena

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    You get the squared magnitude of a vector if you take the dot product of that vector with itself.
    This is always positive (for a non-zero vector).

    A dot product between 2 different vectors can be negative.
    This indicates that the angle between the vectors is greater than 90 degrees.
  4. Jan 23, 2012 #3
    Thanks I like Serena, this cleared up the confusion.
  5. Jan 23, 2012 #4

    I like Serena

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