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    I managed to do parts a) and b) but for part c) I'm stuck on what to do next,
    So far I've taken moments about C to get Wx = 5000. I resolved vertically to get 1000 + Rc = W (Rc is reaction force of C). I then tried moments about W and got Rc(x) = 5000 - 1000x this didn't help either.

    I can't seem to find the weight from this, is there something I missed out? thank you
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    (Original post by .raiden.)
    I managed to do parts a) and b) but for part c) I'm stuck on what to do next,
    So far I've taken moments about C to get Wx = 5000. I resolved vertically to get 1000 + Rc = W (Rc is reaction force of C). I then tried moments about W and got Rc(x) = 5000 - 1000x this didn't help either.

    I can't seem to find the weight from this, is there something I missed out? thank you
    First of all, taking moments about C was a good idea. That gives you an equation with two variables, which immediately suggests that you need another equation with the same two variables.

    You should realise that taking moments about C was a good idea precisely because it got rid of Rc. You therefore do not want an equation with Rc in it at all, so although you resolved forces correctly, the equation is not useful in this question.

    Therefore you should look back to the setup from part (a). You were given an assumption that the log was uniform, but you are now told that it is unlikely to be so. So you revisit the case where the force is being applied at A and this time take moments about D which will give you an equation in terms of W and x. You then have a simple case of simultaneous equations, from which W and x should drop out pretty quickly.
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    (Original post by Brister)
    First of all, taking moments about C was a good idea. That gives you an equation with two variables, which immediately suggests that you need another equation with the same two variables.

    You should realise that taking moments about C was a good idea precisely because it got rid of Rc. You therefore do not want an equation with Rc in it at all, so although you resolved forces correctly, the equation is not useful in this question.

    Therefore you should look back to the setup from part (a). You were given an assumption that the log was uniform, but you are now told that it is unlikely to be so. So you revisit the case where the force is being applied at A and this time take moments about D which will give you an equation in terms of W and x. You then have a simple case of simultaneous equations, from which W and x should drop out pretty quickly.
    Thank you i will try this now
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    (Original post by Brister)
    First of all, taking moments about C was a good idea. That gives you an equation with two variables, which immediately suggests that you need another equation with the same two variables.

    You should realise that taking moments about C was a good idea precisely because it got rid of Rc. You therefore do not want an equation with Rc in it at all, so although you resolved forces correctly, the equation is not useful in this question.

    Therefore you should look back to the setup from part (a). You were given an assumption that the log was uniform, but you are now told that it is unlikely to be so. So you revisit the case where the force is being applied at A and this time take moments about D which will give you an equation in terms of W and x. You then have a simple case of simultaneous equations, from which W and x should drop out pretty quickly.
    Yes i got the answer, i really need to always look at previous parts as this never occured to me

    Thanks for the reply again
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    (Original post by .raiden.)
    Yes i got the answer, i really need to always look at previous parts as this never occured to me

    Thanks for the reply again
    Hey, if you can improve a little after every question you do, then you are studying effectively

    This is quite a neat question, really. You should always try to understand why the questions ask you to do certain things. The reason they apply a force until the log is about to tip is that you get rid of one of the reaction forces. You then basically ignore the other reaction force by taking moments about the axis through the contact. You cannot find W or x from one equation, so you just repeat the procedure at the other end.
 
 
 
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