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Homework Help: What does it mean vector in the positive dirction of the y-axis.

  1. Oct 6, 2011 #1
    1. The problem statement, all variables and given/known data
    If vector a is added to vector b = 7.4i + 7.7j, the result is a vector in the positive direction of the y axis, with a magnitude equal to that of vector b. What is the magnitude of vector a?


    2. Relevant equations



    3. The attempt at a solution
    (Is the vector in the positive direction of the y-axis same positive direction of x-axis?
    cosθ=u.v/||u|| ||v||
    ||ab||=5=||b||.
     
    Last edited: Oct 6, 2011
  2. jcsd
  3. Oct 6, 2011 #2

    NascentOxygen

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    Positive direction of the y axis is: pointing straight up. :smile:

    Positive direction of the x axis is: in a direction horizontally to the right.

    This assumes the usual x-y orientation, with y axis vertical, and x axis horizontal.
     
  4. Oct 6, 2011 #3

    Does it mean the vector of a,b,and ab are pointing in the same direction? Therefore, the angle of the c is lying on x-axis or y=axis ? :)
     
  5. Oct 6, 2011 #4
    May I have some hints for this question ?
    :)
     
  6. Oct 6, 2011 #5

    NascentOxygen

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    No. (Mind you, I don't know what you mean by "the vector of a,b,and ab", but the answer is still no.) :smile:

    In fact, I don't know what you mean by "b = 7.4 + 7.7" either. What do you think you mean?
     
  7. Oct 6, 2011 #6
    I'm sorry for my "hanging" sentences. ( b=7.4i + 7.7j ).
     
  8. Oct 6, 2011 #7
    The question is fixed. :)
     
  9. Oct 6, 2011 #8

    NascentOxygen

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    And what about the answer? Also fixed?
     
  10. Oct 6, 2011 #9
    Unfortunately, no. I'm still thinking. I would be appreciate if you can help me out . :) thank you.
     
  11. Oct 6, 2011 #10

    SammyS

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    A vector in "the positive direction of the y axis" will be in the form of pj, where p > 0 .
     
  12. Oct 7, 2011 #11

    NascentOxygen

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    Draw a set of axes. Draw an arrow representing vector B. Now, add another vector to the end of B, of a magnitude & direction that makes the resultant sum to be a vector that points vertically upwards.
     
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