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    Solving in the direction of 2N, the answer is 2 - 5cos30 - Psina

    I have no idea how they got 5cos30 in the opposing direction. I've filled in the angles and 5N has no relation to 30 degrees??? Nor does Psina. I see the cos90-a is sina but why have they used Psina, it's not even going in that direction!
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    (Original post by ps1265A)


    [Res]olving in the direction of 2N, the answer is 2 - 5cos30 - Psina

    I have no idea how they got 5cos30 in the opposing direction. !
    It's the component of the 5N force perp to the plane.
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    (Original post by atsruser)
    It's the component of the 5N force perp to the plane.
    That could be either -5cos60 or -5cos120, which one?

    And what about Psina? It as no contribution to the vertical force
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    (Original post by ps1265A)
    That could be either -5cos60 or -5cos120, which one?

    And what about Psina? It as no contribution to the vertical force
    You're resolving perpendicular to the plane - if you extend the line of the 2N force downwards through the plane you can see where the 30 degree angle comes from.

    And Pcos(90 - a) = Psina is the component of the P force along the line where the 2N force is acting.

    I'm not entirely convinced by the 'answer' you quoted in your first post - I would expect to see something like Psina + 2 = 5cos30 but that may be just me reading the diagram wrong!
 
 
 
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