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Resultant Force of two vectors

  1. Oct 5, 2014 #1
    Hibbler.ch2.p69.jpg

    Find the result force of the two forces.
    This problem seemed easy at first, but I think I'm confused as to how to find the coordinate angle (gamma) . For the ( i,j,k) components of F1, I got (300cos(30)i, 0j, 300sin(30)k) I don't understand the function of the 45 degree angle, either. What am i doing wrong? Is the 45 degrees the angle between the y axis and F2? and also would that make 135 degrees the angle between F2 and Z? then that would make 60 degrees the angle between the x-axis and F2. However, the answer for the resultant force is 733... and i got a number close to 900.
     
  2. jcsd
  3. Oct 5, 2014 #2

    phinds

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    Interpretation of the figure seems pretty straight-forward to me. F2 is 30 degrees down from the y axis on the yz plane and if you create a plane that is perpendicular to the yz plane and contains the F2 vector, F2 is out 45 degrees put on that plane from the line it makes with the yz plane. F1 is obviously 30 degrees down from the x axis on the xz plane.
     
  4. Oct 5, 2014 #3

    SteamKing

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    Please post HW-type problems like this in the appropriate HW forum. Also, please use the HW template.
     
  5. Oct 5, 2014 #4
    New to this site, Sorry.
     
  6. Oct 5, 2014 #5
    I look at it from a different, but equivalent, perspective. The force F2 makes an angle of 45 degrees with the x-y plane. Its projection onto the x-y plane makes an angle of 30 degrees with the y axis and 60 degrees with the x axis.

    Chet
     
  7. Oct 5, 2014 #6

    phinds

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    HA ... you are right of course. An optical illusion, sort of. Seems totally open to interpretation.
     
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