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    god! this is so confusing!
    P135 M2 Edexcel

    6 A uniform rod AB of length 4m and mass 4 kg is freely hinged at A to a vertical wall. A force P is applied at B at right anles to the rod in order to keep the rod in equilibirum at an angle of 30 degrees to the horizontal, as shown

    Find a) the magnitude of P
    b) the magnitude of R, the reaction of the hinge.


    hm i think ive done the first bit right;
    a) taking moments about A
    2(4g)(cos 30) = 4P
    P = 17.0 N which is what thye get

    but then b) is a total mind****.

    thanks for any help
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    you have to use both moments and newtons 1st law.
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    (Original post by elpaw)
    you have to use both moments and newtons 1st law.
    1st?! You mean 3rd right?
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    (Original post by Nylex)
    1st?! You mean 3rd right?
    no, 1st. i.e. all the forces will be balanced if there is an equilibrium
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    (Original post by elpaw)
    no, 1st. i.e. all the forces will be balanced if there is an equilibrium
    Argh ok.
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    (Original post by elpaw)
    you have to use both moments and newtons 1st law.
    yup i got that far, it was more the calculating momentst that got me.
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    (Original post by kikzen)
    god! this is so confusing!
    P135 M2 Edexcel

    6 A uniform rod AB of length 4m and mass 4 kg is freely hinged at A to a vertical wall. A force P is applied at B at right anles to the rod in order to keep the rod in equilibirum at an angle of 30 degrees to the horizontal, as shown

    Find a) the magnitude of P
    b) the magnitude of R, the reaction of the hinge.


    hm i think ive done the first bit right;
    a) taking moments about A
    2(4g)(cos 30) = 4P
    P = 17.0 N which is what thye get

    but then b) is a total mind****.

    thanks for any help
    ok for b), if you have the reaction force as R_h (horizontal component) and R_v (vertical component)

    R_h = Psin30 = 8.5N

    R_v = Pcos30 - 4g = -24.47N

    |R| = sqrt(R_h² + R_v²) = 25.91 N
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    Take vertical and horizontal components and solve trigonometric simultaneous equations? Draw a force diagram?
 
 
 

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