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Chels
Lv 5
Chels asked in Science & MathematicsMathematics · 1 decade ago

Help with a trigonometry problem?

Two forces of 631 lbs and 172 lbs act on a point. If the angle between the forces is 70 degrees, find the magnitude of the resultant force to the nearest tenth. Also, show how you got the answer. Thanks!

1 Answer

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  • Ron W
    Lv 7
    1 decade ago

    I want to do this one with vectors.

    Since the coordinate system used cannot affect the result, let the 631 lb force act in the direction of the +x axis, and let the 172 lb force vector lie in the first quadrant such that it makes a 70° angle with the first vector.

    Then these forces are given by 631 i and 172 cos(70°) i + 172 sin(70°) j . Their sum S is given by

    S = (631 + 172 cos(70°)) i + 172 sin(70°) j

    |S| = √[(631 + 172 cos(70°))² + (172 sin(70°))²]

    I leave the calculation to you.

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