Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Unit vectors please check my answer

  1. Jan 30, 2012 #1
    1. The problem statement, all variables and given/known data
    if [itex]\vec{e_{1}}[/itex] = 5[itex]\hat{i}[/itex] - 3[itex]\hat{j}[/itex] + 2[itex]\hat{k}[/itex] what is the unit vector [itex]\hat{e_{1}}[/itex]


    2. Relevant equations



    3. The attempt at a solution
    here is my answer,, please confirm if i'm correct.

    [itex]|[/itex][itex]\hat{e_{1}}[/itex][itex]|[/itex] = [itex]\sqrt{\vec{e_{1}} . \vec{e_{1}}}[/itex]
    [itex]|[/itex][itex]\hat{e_{1}}[/itex][itex]|[/itex] = [itex]\sqrt{(5\hat{i} - 3\hat{j} + 2\hat{k}) . (5\hat{i} - 3\hat{j} + 2\hat{k})}[/itex]
    [itex]|[/itex][itex]\hat{e_{1}}[/itex][itex]|[/itex] = [itex]\sqrt{(5\hat{i}) . (5\hat{i}) + (-3\hat{j}) . (-3\hat{j}) + (2\hat{k}) . (2\hat{k})}[/itex]
    [itex]|[/itex][itex]\hat{e_{1}}[/itex][itex]|[/itex] = [itex]\sqrt{(25+9+4)}[/itex]
    [itex]|[/itex][itex]\hat{e_{1}}[/itex][itex]|[/itex] = [itex]\sqrt{38}[/itex]


    [itex]\hat{e_{1}}[/itex] = [itex]\frac{5\hat{i} - 3\hat{j} + 2\hat{k}}{\sqrt{38}}[/itex]

    am i correct? Please check
     
    Last edited: Jan 31, 2012
  2. jcsd
  3. Jan 30, 2012 #2

    SammyS

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    That's not a unit vector.

    Please state the problem you're trying to solve.
     
  4. Jan 31, 2012 #3
    sorry i wasn't finished editing yet earlier.. please check my solution now. Thanks :))
     
    Last edited: Jan 31, 2012
  5. Jan 31, 2012 #4

    SammyS

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    Yes. That is correct .
     
  6. Jan 31, 2012 #5
    Thanks.. Can you please check my other question.. I really appreciate it! Thanks again.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook