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Just Tell Me If Its Doable (Vectors)

  1. Oct 12, 2008 #1
    Just Tell Me If Its "Doable" (Vectors)

    Here's the problem:
    Give magnitude and direction from the positive x axis, given A=60. Use the following picture:

    http://www.webassign.net/giancoli5/3_35alt.gif

    I know how to do vectors...
    Ax: 60cos(28)=52.98
    Ay: 60sin(28)=28.17

    Cx: 0
    Cy: 46.8

    B: ?
    B: ?

    Now correct me if I am wrong, but don't I need the angle of B in order to solve?
     
  2. jcsd
  3. Oct 12, 2008 #2

    Doc Al

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    Staff: Mentor

    Re: Just Tell Me If Its "Doable" (Vectors)

    What's the exact statement of the problem?
     
  4. Oct 17, 2008 #3
    Re: Just Tell Me If Its "Doable" (Vectors)

    Determine the vector A - C, given the vectors A and C in Fig. 3-35 (A = 60.0).

    Magnitude:_____
    Direction:____ ° (from the positive x axis)
     
  5. Oct 17, 2008 #4

    Doc Al

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    Staff: Mentor

    Re: Just Tell Me If Its "Doable" (Vectors)

    This has nothing to do with B, so B's angle is not needed.

    Good, except for the sign of Cy.
     
  6. Oct 20, 2008 #5
    Re: Just Tell Me If Its "Doable" (Vectors)

    Oh ok I got it now. Since its A-C, I just take my C values and times them by -1. So now I have,
    C=-46.8(-1)=46.8 (y)
    C=0 (x)

    And then I take the values Rx and Ry:

    Rx: 52.98
    Ry: 74.97

    And plug in the formula:

    squareroot(52.98^2+74.97^2)=91.8

    And I get my angle:

    tan-1(74.97/52.98)=54.8

    Yay!!!
     
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