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Homework Help: Addition of Vectors

  1. Sep 23, 2004 #1
    One of my review questions is the following:

    "A box is pulled along the floor by a horizontal force of 35 N. Another force acts concurrently on the box with a force of 25 N at an angle of 40 degrees above the horizontal in the same direction as the first force. What is the sum of the two vectors?"

    I got the magnitude of the vector to be 56 N by finding the square root of the horizontal and vertical components respectively squared. However, how does one find the angle. I know I need to calculate the inverse tangent of something - but what?
     
  2. jcsd
  3. Sep 23, 2004 #2
    Try breaking the vectors down into their x and y components. Then find the sum of the x components, then the sum of the y components. Then, draw a triangle with these vector sums and use trig to find the resultant vector.
     
  4. Sep 23, 2004 #3
    thanks...I'll definetely do better on the exam now :cool:
     
  5. Sep 23, 2004 #4
    glad I could help! :smile:
     
  6. Sep 23, 2004 #5
    note be sure to add in the extra degres when using a triangle for trig
    you can solve for the angle but then you may need to add/subtract 90,180,270,360
     
    Last edited: Sep 23, 2004
  7. Sep 23, 2004 #6
    example
    --------------=--------------------
    --------------=-------------------- ROUGH DRAWING
    --------------=--------------------
    --------------=-------------------- VECTOR ONE= postive x
    --------------=-------------------- VECTOR TWO= negitive y
    --------------=--------------------
    ============AAAAAAAAAAAAAAA
    --------------A-A------ If you solve for this angle and you have
    --------------A-- A----------counterclockwise movement then you must
    --------------A----- A------- subtract 360 to get angle
    --------------A-------- A
    --------------=-------------------
    --------------=-------------------
    --------------=-------------------

    I hope this makes sense
    i know it is very rough sketch
     
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