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Math Help - Resultant Force

  1. #1
    Tek
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    Resultant Force

    Forces with magnitudes of 85 pounds and 50 pounds act on a single point. The angle between the forces is 15 degrees. Describe the resultant force.

    The answer in the book is: "The resultant force is 113.92 pounds and 5.6 degrees from the 85-pound force."

    For the life of me I cannot understand how to obtain this answer though...
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  2. #2
    Eater of Worlds
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    Is there a diagram to go along with the problem?. That may help.

    Try the law of cosines.

    75+\sqrt{85^{2}+50^{2}-2\cdot 85\cdot 50\cdot cos(15)}\approx 113.92
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  3. #3
    No one in Particular VonNemo19's Avatar
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    Now go solve this thing!

    Hey Tek, A parrallelogram is formed from the two added force vectors. The law of cosines is all you need to solve this problem.

    (you can solve for a to make your life easier)

    So let alpha be equal to 165 (365-15-15 because you need that angle to use this formula) and let b and c be be the sides ajacent to the angle and let b=the resultant vector. I'm pretty sure that's all ya need.

    If youneed more help let me Know!
    Last edited by VonNemo19; April 25th 2009 at 05:36 PM. Reason: forgot something
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