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Thread: Resolving forces

  1. #1
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    Resolving forces

    Hey guys,
    Question: A mass of 2.6 kg is maintained in equilibrium in a vertical plane by forces of 5P N and 12P N (where P is an unknown constant) which are perpendicular.
    5P is at an angle $\displaystyle \alpha $ from the vertical.
    Find the value of $\displaystyle \alpha $ and the value of the constant P.

    So 12p is at an angle of $\displaystyle 90-\alpha $ from the vertical. (My reasoning)

    Resolving vertically I get: $\displaystyle 5p\cos \alpha + 12p\sin \alpha =26$
    And horizontally: $\displaystyle 12p\cos \alpha = 5p\sin \alpha $

    After that I'm stuck, simultaneous equations I presume.
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  2. #2
    Senior Member abhishekkgp's Avatar
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    Quote Originally Posted by elieh View Post
    Hey guys,
    Question: A mass of 2.6 kg is maintained in equilibrium in a vertical plane by forces of 5P N and 12P N (where P is an unknown constant) which are perpendicular.
    5P is at an angle $\displaystyle \alpha $ from the vertical.
    Find the value of $\displaystyle \alpha $ and the value of the constant P.

    So 12p is at an angle of $\displaystyle 90-\alpha $ from the vertical. (My reasoning)

    Resolving vertically I get: $\displaystyle 5p\cos \alpha + 12p\sin \alpha =26$
    And horizontally: $\displaystyle 12p\cos \alpha = 5p\sin \alpha $

    After that I'm stuck, simultaneous equations I presume.
    from the second equation you get the value of $\displaystyle \tan \alpha =12/5$. hence $\displaystyle \sin \alpha=12/13$ and $\displaystyle \cos \alpha = 5/13$ (why?).
    substitute in above.
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  3. #3
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    didn't see that!
    Thank you!
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