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Calculating a value of force using vectors?

  1. Feb 11, 2009 #1
    A box is being pulled with a resultant force of (33i+96j)N by 3 people. Another person starts pulling the box with a force of (100i+pj)N. With all 4 people pulling the box, it moves in the direction of (12i +j). I need to work out the value of p.

    For this would I add 100 and 33, and then divide by 12 to find the proportions of i. And then with that times it by the 1j to get what j is.
    E.g.
    100+33=133
    133/12=11.1

    1x11.1=11.1
    96+j=11.1
    j= -84.9

    Or is this totally wrong?

    Any help at all would be greatly appreciated. Many Thanks!
     
  2. jcsd
  3. Feb 11, 2009 #2

    Delphi51

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    Correct!
    Might be easier to follow if you put
    33i+96j + 100i+pj = k(12i+j)
    Separate the i part from the j part. Use the i part to evaluate k, then use it in the j part to find p.
     
  4. Feb 11, 2009 #3

    LowlyPion

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    That looks correct. Of course you are finding p and not j, but the method looks ok.
     
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