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    https://3b0a7b1bc87f5381e60f8f717510...%20Edexcel.pdf

    for 6c)of this question,how do you work out k? Please give simple explanation only as it will confuse me even more. Thanks
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    Try to provide what you have attempted. There is a weight where the string at b is under zero tension. This is the maximum value of k. Any k lower than this will mean that both strings are taking some weight rather than the rod pivoting about c.
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    (Original post by nerak99)
    Try to provide what you have attempted. There is a weight where the string at b is under zero tension. This is the maximum value of k. Any k lower than this will mean that both strings are taking some weight rather than the rod pivoting about c.
    HI, this is what I did. Please could you show me a diagram for the explanation? Thanks.Name:  1456831198549-1268971868.jpg
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    Name:  img002.jpg
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    Your diagram is fine although I would have neglected using 'N' in the labels as I think that the N confuses things as it looks like a variable.

    My calculation is different though \frac{2}{3}W=2R_b + kW \;\;\Rightarrow\;\; T=\frac{W}{2}\left(\frac{2}{3}-k \right) You have put kW i the wrong direction (as you are equating CW and ACW moments, the moment at D is CW).

    Once you have done this we can see that R_b is zero when
    k=\frac{2}{3}
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