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Homework Help: Vector addition question

  1. Mar 5, 2014 #1
    1. The problem statement, all variables and given/known data

    If vector A + vector B = vector C and magnitude A + magnitude B = magnitude C how are vector A and B relative to each other.

    2. Relevant equations

    3. The attempt at a solution

    I need help understanding this question. I know that in order for them to be equal they must be in the same direction. Also, does this mean that the vectors form a right angle to teach other in order for he magnitudes to be equal. Please help me, I'm so confused.
  2. jcsd
  3. Mar 5, 2014 #2
    Try to draw a diagram which shows that mag A + mag B = mag C.
  4. Mar 5, 2014 #3
    Yes, you're right that since the magnitudes of A and B add up to C, then all three vectors must be in the same direction. Not quite sure what you mean by the vectors forming a right angle -- they'll just all be in the same direction. Knowing that, how would A and B line up to form C?
  5. Mar 5, 2014 #4
    But what would be the relationship between the two vectors? How can I prove that they are equal?
  6. Mar 5, 2014 #5
    But you don't know that A and B are equal -- only that they add up to C. I think the question just asks how A and B are oriented relative to each other.
  7. Mar 5, 2014 #6
    So when drawing out the vector and magnitude diagrams, they both would look exactly alike?
  8. Mar 5, 2014 #7
    But that would mean that A and B are equal in magnitude, which you don't know. Did you draw out the diagram? If you just draw A and B to have arbitrary lengths (so long as they add up to C), what else can you say about A and B in terms of orientation?
  9. Mar 5, 2014 #8
    Im not sure. It comes out to be a triangle?
  10. Mar 5, 2014 #9
    Usually that's what vector addition looks like, but is that the case for here? If A and B are sides of a triangle, and if C is the the other, longest side, then what happens when A and B add up to C?
  11. Mar 5, 2014 #10
  12. Mar 5, 2014 #11
    If you could do some more explaining with words, that would help out -- that formula isn't really relevant here. Just talk about what you think will happen if two sides of a triangle add up to the third side. Try to draw a picture of it.
  13. Mar 5, 2014 #12
    I think that A and B would add up to make the resultant vector C. That means A and B would be perpendicular to each other.
  14. Mar 5, 2014 #13
    Not necessarily though. In that case A, B, and C would form a right triangle, but you also have to have |A| + |B| = |C| (|A| means magnitude of A), in which case a right triangle wouldn't work, since you can't add the legs of a right triangle to get the hypotenuse.
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