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Math Help - vector help

  1. #1
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    vector help

    Three vectors a, b and c are each 50m long and lie in the x-y place. Their directions relative to the positive x axis are 30 degree, 195 degree and 315 degree respectively. what are the magnitude and angle of a + b + c, and of a - b + c. What are the magnitude and angle of a fourth vector d such that (a + b) - (c + d) = 0.

    I took the angle between the two vectors a and b as 195 - 30 = 165 and tried to apply parallelogram law of addition for a and b. and c could be added to a + b.

    Is the method correct? The problem is I am not able to do anything with the angle 165 degree.

    How to do this problem. Any help?

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  2. #2
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    Re: vector help

    Not sure that you can find the sum of the vectors using the parallelogram law (someone may correct me). I would find the x,y components of the vectors and then do simple vector addition. So for a you have an angle of 30 and a hypotenuse of 50. Use plain old trig to get x and y. Do the same for the others.
    Thanks from topsquark
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  3. #3
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    Re: vector help

    ok. For 30 degree, it would be easy. What about 195 degree and 315 degree?
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  4. #4
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    Re: vector help

    Well 195 gives you a triangle with an angle of 15 from the horizontal. You should be able to figure out the x,y components.
    Thanks from arangu1508
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