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QUICK question concerning RESULTANTS with FORCE

  1. Oct 3, 2006 #1
    http://img.photobucket.com/albums/v170/sleepyboixcl/physics.jpg


    thats the picture.


    The question reads "What is the resultant of these two forces?"



    My idea is that you would treat the lines like vectors and break it up into components to solve for the resultant. I have been trying fruitlessly however for about 30 minutes, my foundation in vector addition is very weak. If someone could point me in the right direction i would very much appreciate it!
     
  2. jcsd
  3. Oct 3, 2006 #2

    Andrew Mason

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    I am not sure what the dotted line represents. In order to give any meaning to direction you need a reference frame. Assuming the dotted line is North, say, then the dotted line and a line perpendicular to it would be a reasonable reference frame.

    Find the components of each vector in the North-South direction, add them. Then find the component of each vector along the East-West and add them. Then add the squares of those components and take the square root to find the length. The direction is given by the components.

    The north-south component of the left vector is 450 cos(10)N and its east-west component is 450 sin(10)W. I think you can do the rest.

    AM
     
  4. Oct 3, 2006 #3

    no, i cant:cry:


    i am a bumbling idiot when it comes to adding vectors and finding components.. am i trying to make right triangles to find each side? i still really dont understand. And could you explain the sin/cos to me as well? my teacher was absent during the whole vector portion:grumpy:
     
  5. Oct 3, 2006 #4

    Andrew Mason

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    Well you have to know a little trigonometry. We aren't going to teach you that here, but essentially you make a right triangle of each vector with the NS/EW axes. You project the vector onto each axis to find its components. The length of the side of the triangle opposite the angle is Lsin(angle) where L is the vector length. The length of the side adjacent to the angle is Lcos(angle). That is just a definition of these two trigonmetric functions. (cos = adjacent side/hypotenuse; sin = opposite/hypotenuse).

    AM
     
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