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Math Help - Need help with angles

  1. #1
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    Need help with angles

    Two equal forces act on an object at 80 degree to on another. the resultant force has a magnitude of 100 N. What are the forces.
    This is what I did


    not sure what to do after
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  2. #2
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    Quote Originally Posted by supersaiyan View Post
    Two equal forces act on an object at 80 degree to on another. the resultant force has a magnitude of 100 N. What are the forces.
    This is what I did


    not sure what to do after
    Use the Cosine rule to calculate the equal forces:

    Let f denote the magnitude of the forces. Then solve for f:

    100^2=f^2+f^2-2\cdot  f \cdot f \cdot \cos(100^\circ)

    I've got f \approx 65.27\ N
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  3. #3
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    Quote Originally Posted by earboth View Post
    Use the Cosine rule to calculate the equal forces:

    Let f denote the magnitude of the forces. Then solve for f:

    100^2=f^2+f^2-2\cdot  f \cdot f \cdot \cos(100^\circ)

    I've got f \approx 65.27\ N
    Thanks, I got the same thing
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  4. #4
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    Sorry, I got one more question

     |\overrightarrow{u}|=110, |\overrightarrow{v}|=75 and the angle between  \overrightarrow{u} and \overrightarrow{v} (when placed tail to tail) is 100^\circ. Find |\overrightarrow{u} + 3\overrightarrow{v}|
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  5. #5
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    Quote Originally Posted by supersaiyan View Post
    Sorry, I got one more question

     |\overrightarrow{u}|=110, |\overrightarrow{v}|=75 and the angle between  \overrightarrow{u} and \overrightarrow{v} (when placed tail to tail) is 100^\circ. Find |\overrightarrow{u} + 3\overrightarrow{v}|
    1. If you have a new question start a new thread. Otherwise you risk that nobody will notice your need for help.

    2. Use the Cosine rule:

    l = \sqrt{110^2+(3 \cdot 75)^2-2\cdot 110 \cdot 3 \cdot 75 \cdot \cos(100^\circ)}

    I've got l \approx 261.6
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