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Homework Help: Unit Vector

  1. May 3, 2012 #1
    1. The problem statement, all variables and given/known data

    Given vector OP = 2i+3j, OQ = qi+2qj. How can i find the possible value for q?
    note that PQ is a unit vector.

    2. Relevant equations

    Given (p-1)i + (2p-6)j having magnitude 10, find p

    3. The attempt at a solution

    From the formula, i was told that the unit vector can be obtain by dividing the vector by the modulus it self, however i have no idea how to apply that concept into 2 different vector, since the answer wasn`t correct when i tried them. please help me on this, thanks in advanced
  2. jcsd
  3. May 3, 2012 #2


    Staff: Mentor

    So what are the coordinates of PQ? You have OP and OQ, so you should be able to find PQ.

    Once you have found PQ, figure out what q needs to be so that PQ is a unit vector.

    This part -- Given (p-1)i + (2p-6)j having magnitude 10, find p -- is a separate problem, right? How you have presented these problems is confusing.
  4. May 4, 2012 #3
    it is actually hint given to me as how that i`m going to solve the q part, where it is also having two vector with one of it having p variable. i have no idea how it works either. as for the PQ, the question doesn`t state whether its P to Q or Q to P. so it is safe for me to take it as P to Q?
  5. May 4, 2012 #4


    Staff: Mentor

    PQ means from P to Q. If the question asked for the vector from Q to P, they would have specified QP.
  6. May 4, 2012 #5
    ok, thanks
  7. May 4, 2012 #6


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    By the way, Eryk: Welcome to PF !
  8. May 5, 2012 #7
    Thanks :)
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