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Homework Help: Vector 2B - Vector A (graphical method)

  1. Sep 15, 2008 #1
    1. The problem statement, all variables and given/known data

    Vector A is 4.00 units and 40* below x-axis. Vector B is 3.00 units and 25* below -x-axis. Use the graphical method (only ruler and protractor) to find Vector 2B - Vector A. I have to find the magnitude and direction.

    When I did it I got 8.5 and East, but I'm not sure if I did it right. When they say 4.00 and 3.00 units, is that the ax component of the vector? That's the way I did it. I drew out the vector then measured 3 and 4 units on the ax comp. of both vectors, then measured from that point down to the vector and got the ay component. Then I just solved for the magnitude.

    thanks
     
  2. jcsd
  3. Sep 15, 2008 #2

    LowlyPion

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    The vector length is 4 at an angle of 40 degrees down below positive X axis and the other vector is 3 long pointing down from the negative x-axis. (The other direction of x)

    But they say 2*B which makes that vector 6 long.
     
  4. Sep 15, 2008 #3
    ok i just redrew it and now im lost. im getting confused about what theyre asking
     
  5. Sep 15, 2008 #4

    LowlyPion

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    You've drawn the two vectors - doubling B?

    Then reverse Vector A - same length - opposite direction.

    They say 2*B - A right. This is vector subtraction. But you do that by "adding" the negative of the Vector A.

    Now add these two vectors together.
     
  6. Sep 15, 2008 #5
    ok i did it again and im sure i got it wrong again but i got
    2*B-A= -.8i-.6j
    magnitude = 1
     
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