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Find unit vetors satisfying qualifying conditions HELP test tomorrow

  1. Oct 26, 2008 #1
    Find unit vetors satisfying qualifying conditions!!! HELP test tomorrow

    1. The problem statement, all variables and given/known data
    Find the unit vectors satisfying qualifying conditions:

    a. oppositely directed to 3i-4j

    b. same direction as 2i-j-2k

    c. same direction as vector from A(-3,2) to B(1,-1)




    Thoughts.
    Ok. So i don't know where to start. Can someone hint me. I know to find unit vector u must divide each term by the magnitude but the direction stuff isn't helping me. lol
     
  2. jcsd
  3. Oct 26, 2008 #2

    gabbagabbahey

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    Re: Find unit vetors satisfying qualifying conditions!!! HELP test tomorrow

    Call the unit vector [itex]\hat{n}=n_1\hat{i}+n_2\hat{j}+n_3\hat{k}[/itex] and look at what your conditions tell you about [itex]\hat{n}[/itex]...

    (a) directed oppositely to 3i-4j....what is the direction of 3i-4j...what does that mean the direction of [itex]\hat{n}[/itex] is?...remember [itex]\hat{n}[/itex] is a unit vector, so you know its magnitude is 1.

    (b)same direction as 2i-j-2k...what IS the direction of 2i-j-2k?

    (c)what is the vector from A to B?...what is its direction?
     
  4. Oct 26, 2008 #3
    Re: Find unit vetors satisfying qualifying conditions!!! HELP test tomorrow

    Ok. I kinda figured it out. Thanks for the help... But can u check ur answers with me.

    Here are my answers.

    a) (-3/5)i + (4/5)j

    b) (2/3)i - (1/3)j - (2/3)k

    c) (4/5)i - (3/5)j

    Thanks for your time!
     
  5. Oct 26, 2008 #4

    gabbagabbahey

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    Re: Find unit vetors satisfying qualifying conditions!!! HELP test tomorrow

    Looks good to me!:approve:
     
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