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Math Help - vector resultant

  1. #1
    Senior Member euclid2's Avatar
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    vector resultant

    find the magnitude and direction of the resultant of two vectors u and v with magnitudes of 6 and 2 and an angle of 140 between them.

    i got |u+v|=7.64 units and the direction to be 9.69 deg, is it right?
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  2. #2
    MHF Contributor Unknown008's Avatar
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    You can make a sketch, and complete the parallelogram of forces.

    From this, the magnitude of the resultant forces is given by the cosine rule, taking the sides 6 and 2 and the angle (180-140) = 40 degrees.

    Resultant = \sqrt{2^2 + 6^2 - 2(2)(6)\cos(40)}

    Can you try out again on the direction now?
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  3. #3
    Senior Member euclid2's Avatar
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    i get 4.64 units and 16 deg
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  4. #4
    MHF Contributor Unknown008's Avatar
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    That's it!

    Well done.

    Here's a picture to see where the 40 degrees came from:

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