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Homework Help: Vector Addition Help!

  1. Nov 3, 2012 #1
    1. The problem statement, all variables and given/known data
    Alright so i need to add these using vector addition i suppose.
    P = M + N
    P = 1.8304 kgxm/s (S 6° W) + 3.2864 kgxm/s (S 42° W)

    3. The attempt at a solution
    This is my half attempt:

    But i don't know if im doing it right... and how would i find the angle in between, the angle across P....
    .. it would mean alot if someone helped me out with this...
  2. jcsd
  3. Nov 3, 2012 #2
    When you do vector addition, you do it component-wise. You need to find the South and West components of each M and N. Add those together to get the South and West components of P.

    Also, your drawing is incorrect. You have red-South as black-East and red-West as black-South. If you use this as your guide, you will either get the right answer and think it's wrong or get the wrong answer and think it's right.
  4. Nov 3, 2012 #3
    Hey, i am a bit confused about your statement ... In my homework it says use the vector way not the components way.... i think i know what you mean... but how can i use the vector way to find the answer.....
  5. Nov 3, 2012 #4
    And when i was actually doing the drawing.. i tilted the paper and then did my extension of the S 42° W to the 6° angle drawn
  6. Nov 3, 2012 #5
    If you're forced to do it by drawing, you can still confirm using the components.

    When drawing, you have to make sure that your drawings are accurate and to scale. If your drawing on photobucket is like the drawing you made for your homework, you will not get the right answer.
  7. Nov 3, 2012 #6
    Oh.... umm but like how would i find the angle that is opposite to the P... i mean the angle in between i am confused... on that part... well i know there is the 42° but what about the other angle that contributes into that...?
  8. Nov 3, 2012 #7
    You're supposed to find the angle of P from South. Take a protractor, place the center at the tail of P, with 0 degrees pointing South. Measure the angle of P.
  9. Nov 3, 2012 #8
    But what if i were to actually do it algebracally... so like finding the angle that is apposite to p AND then finding the p using cosine law.. and at the end find the angle that of P..
  10. Nov 3, 2012 #9
    If you want to do it algebraically, you have to do it component-wise. There is no other way.
  11. Nov 3, 2012 #10
    We did one question in class... but this question i am having trouble with,,,
  12. Nov 3, 2012 #11
    I highly doubt you did a question like this in class without resorting to components in some way. In class, did you at one point use a tan(something)?
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