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Homework Help: My Vector Enigma

  1. Sep 3, 2006 #1
    My question follows off of the picture attached.

    I have been able to answer both questions, but I still have questions of my own.

    I had to solve them geometrically using the Law of Cosines and the Law of Sines...why is it that I am not able to break it into components using the trig functions?

    Surely it has something to do with the axes not being perpendicular..but what exactly?

    As far as the u axis goes...it's just a direction, independent of v, so I don't understand why I cannot solve it using trig functions multiplied by the magnitude.

    The answer for the second problem, is about 205 N via the Law of Sines:

    Fx = (300*sin(40))/sin(110)

    Why can't I simply do cos(30)*300 ?

    And when I try to implement a normal perpendicular system, I still get the wrong components. What am I doing wrong?

    And how would you solve this analytically with trig functions and not geometrically?

    Thank you so much guys.
     

    Attached Files:

  2. jcsd
  3. Sep 3, 2006 #2
    Also if I shift the bottom axis over 20 degrees to make it perpendicular, and try cos(25)*500 to get the y component, and cos(30)*300 to get the x, then use both to get the magnitude, I actually get a different magnitude than I would have using the Law of Cosines.

    It's a bit less.

    Not understanding why either.
     
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