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Math Help - Statics of rigid bodies

  1. #1
    Super Member craig's Avatar
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    Statics of rigid bodies

    Stuck on the enclosed question.

    I have done the first part, taken moments about A, found P to be 2g cos 30, or 17.0N to 3sf. I am taking g as 9.8N btw.

    What I can't do is the second part, find the magnitude of R. I know that there are reactions at R, horizontal and verticle, I am just having problems resolving them and then working out.

    Any help would be greatly appreciated

    Craig
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  2. #2
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    Opalg's Avatar
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    Quote Originally Posted by craig View Post
    Stuck on the enclosed question.

    I have done the first part, taken moments about A, found P to be 2g cos 30, or 17.0N to 3sf. I am taking g as 9.8N btw.

    What I can't do is the second part, find the magnitude of R. I know that there are reactions at R, horizontal and vertical, I am just having problems resolving them and then working out.
    There are only three forces acting on the rod: the weight 4g, and the forces P and R. If the system is in equilibrium then these forces form a vector triangle, as in the attachment. You can find the magnitude of R by applying the cosine rule in this triangle.
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  3. #3
    Super Member craig's Avatar
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    Quote Originally Posted by Opalg View Post
    There are only three forces acting on the rod: the weight 4g, and the forces P and R. If the system is in equilibrium then these forces form a vector triangle, as in the attachment. You can find the magnitude of R by applying the cosine rule in this triangle.
    Thank you! Not thought/been taught to do it this way, it is a lot simpler than messing around with resolving forces
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