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Math Help - Vector problem. I am confused

  1. #1
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    Vector problem. I am confused

    Can someone point out where I am going wrong?

    The vector in the drawing has a magnitude of 750 units.

    (a) Determine the magnitude of the x and y components of the vector , relative to the black axes.
    Ax = 650 units
    Ay = 375 units

    (b) Determine the magnitude and direction of the x and y components of the vector , relative to the colored axes.
    Ax' = 575 units
    Ay' = 482 units

    My question is why is Ay' not just 750cos50?

    Thanks.
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  2. #2
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    Two reasons: 1. You actually have a negative angle there. 2. It should be the sin function.
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  3. #3
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    So if I plug that in I get -575. Is that correct?
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  4. #4
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    So if I plug that in I get -575. Is that correct?
    I don't think so. What expression are you evaluating?
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  5. #5
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    750sin50 and then making that negative. I don't really think that is correct though because that is just the negative of the x component and that doesn't make sense at all.
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  6. #6
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    I think your confusing has to do with how to measure angles in polar coordinates. From where do you normally measure angles? And what's a positive angle? What's a negative angle?
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  7. #7
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    You measure from what is usually the +x plane on a normal cartesian coordinate system. In this case it is the -y axis. A positive angle is measured in a counter-clock-wise direction and a negative angle is measured in a clock-wise direction
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  8. #8
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    Right. So, relative to the red axes, what is the angle of A?
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  9. #9
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    -40 degrees or 320 degrees.
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  10. #10
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    Right. So what is your expression for x'? y'?
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