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Graphically determine resultant vector displacement

  1. Nov 22, 2012 #1
    1. The problem statement, all variables and given/known data
    Graphically determine the resultant of the following three vector displacements:
    1) 24m, 30 degrees North of East
    2) 28m, 37 degrees East of North
    3) 20m, 50 degrees South of West


    2. Relevant equations



    3. The attempt at a solution
    I have the vectors drawn but I can't figure out how to find the resultant displacement. I can't get a right triangle so I can use the Pythagorean theorem.
     
  2. jcsd
  3. Nov 22, 2012 #2
    The resultant is the vector drawn from the tail of the first to the head of the last vectors.
     
  4. Nov 22, 2012 #3

    lewando

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    If you are solving this graphically, a ruler and protractor will help.
     
  5. Nov 22, 2012 #4
    I know that but I need to have a set of coordinates to go with it, like 40 degrees North of West. The answer is in the back of the book but my teacher needs to see work. I can't figure out how I can find the angle and length.

    Lewando: Everything has to be done with math. My teacher says that a ruler and protractor are not accurate enough.
     
  6. Nov 22, 2012 #5

    lewando

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    Agree that solving this purely "graphically" will have some graphical error. I thought you were constrained by the question. If you are not constrained, then use the component method. As a check, your low-accuracy graphical method result should be close to your component method result.
     
  7. Nov 22, 2012 #6
    Can I ask what the component method is?
     
  8. Nov 22, 2012 #7

    lewando

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  9. Nov 22, 2012 #8

    lewando

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    Maybe you are more familiar with the Law of Cosines method. This is used for adding two vectors that are not at a right angle. If you want to add three vectors using this method, add two of the vectors to find an intermediate resultant. Then use the same method to add the third vector to the intermediate resultant to get the final resultant. Here is another good link:
     
    Last edited by a moderator: Sep 25, 2014
  10. Nov 23, 2012 #9
    Did you get the resultant displacement's distance and direction graphically?
     
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