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    Hi, I am not sure how to solve this question, any help is appreciated.

    Two uniform rods XY and YZ, each of weight 20N and length 80cm, are connected by a smooth pin joint at Y. They rest symmetrically on two smooth pegs P and Q at the same level, with angle XYZ =90 degrees. Show that P and Q are approximately 28 cm apart and find the magnitude of the force from the pin on each rod.

    Thanks for the help
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    (Original post by HashBrowns)
    ...
    Diagram.

    Then what are you able to deduce from the question?
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    Both reaction forces are equal? And how would I know which direction they would be in?
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    (Original post by HashBrowns)
    Both reaction forces are equal? And how would I know which direction they would be in?
    Which reaction forces are you refering to?

    Edit: Hinge or pegs?
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    Pegs
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    (Original post by ghostwalker)
    Which reaction forces are you refering to?

    Edit: Hinge or pegs?
    Pegs
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    (Original post by HashBrowns)
    Pegs
    And the pegs are smooth, so what direction is the reaction?

    PS: I presume you've drawn a diagram.
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    (Original post by ghostwalker)
    And the pegs are smooth, so what direction is the reaction?

    PS: I presume you've drawn a diagram.
    I think it would be perpendicular to the rods.
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    (Original post by HashBrowns)
    I think it would be perpendicular to the rods.
    Yep. It can't have any component along the rod, as the peg is smooth.
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    (Original post by ghostwalker)
    Yep. It can't have any component along the rod, as the peg is smooth.
    How about the reaction forces at the hinge?
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    (Original post by HashBrowns)
    How about the reaction forces at the hinge?
    Bearing in mind the symmetry of the situation, consider, can there be a vertical component to the reaction at the pin?
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    (Original post by ghostwalker)
    Bearing in mind the symmetry of the situation, consider, can there be a vertical component to the reaction at the pin?
    I think there isn't a vertical component as otherwise the forces wouldn't balance out considering each rod separately. Not sure though.
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    (Original post by HashBrowns)
    I think there isn't a vertical component as otherwise the forces wouldn't balance out considering each rod separately. Not sure though.
    That's correct.

    If there was a vertical component in one rod, there would have to be a similar vertical component in the other by symmetry, but equally there would have to be an equal and opposite force, by Newton's Laws.

    So, V=V and V=-V hence V=0.

    So only a horizontal force exists.
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    (Original post by ghostwalker)
    That's correct.

    If there was a vertical component in one rod, there would have to be a similar vertical component in the other by symmetry, but equally there would have to be an equal and opposite force, by Newton's Laws.

    So, V=V and V=-V hence V=0.

    So only a horizontal force exists.
    I got F = 20N, and think this is correct. Could you answer the question on my new thread? Thank you very much for the help.
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    (Original post by HashBrowns)
    I got F = 20N, and think this is correct. Could you answer the question on my new thread? Thank you very much for the help.
    Agreed.
 
 
 
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