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Homework Help: Seeking help for vector problem

  1. Jan 26, 2005 #1
    If B is added to C= 3.0i + 4.0j, the result is a vector in the positive direction of the y-axis, with a magnitude equal to that of C. What is the magnitude of B?....... Solution, i got Rx= Ax+Bx+Cx , = (3.0i) and, Ry= Ay+By+Cy, = (4.0j)

    So, the square root of (3.0)2 + (4.0)2 = ....... (5).....for the magnitude of B..... iam i headed in the right direction or am i completely off......... :confused:
     
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  3. Jan 27, 2005 #2

    Galileo

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    You are given that the direction of the resultant is in the positive y-direction.
    So R has the form: [itex]\vec R=A\vec j[/itex]. For some A.
     
  4. Jan 27, 2005 #3

    HallsofIvy

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    Okay: B+ C= R where C= 3 i+ 4 j (which has magnitude 5). You are told that the resultant vector, R, "is a vector in the positive direction of the y-axis, with a magnitude equal to that of C". You then write that "Rx= Ax+Bx+Cx , = (3.0i) and, Ry= Ay+By+Cy, = (4.0j)" which I don't understand at all. Presumably Bx and Cx are x components of B and C, but what is A?

    The vector in the positive direction of the y-axis with magnitude 5 (that of C) is
    5j. Your equation is B+ 3i+ 4j= 5j. All you have to do to find B is subtract 3i+ 4j from both sides of the equation.
     
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