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M2 - Elasticity watch

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    I'm on question 14 below. The answer for AM is 2.99m but I'm getting 2.96m.

    What am I not doing properly, please?
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    (Original post by maggiehodgson)
    I'm on question 14 below. The answer for AM is 2.99m but I'm getting 2.96m.

    What am I not doing properly, please?
    I'm not sure where you have gone wrong but I would have considered e_1+e_2=1.

    My equation for this problem is \dfrac{100(x-2)}{2}-20(4-x-1)=5g. This leads to the solution you gave. Can you see how I obtained this?

    Hope this helps but if not hang on for ghostwalker's always superior explanation.
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    (Original post by BabyMaths)
    Hope this helps but if not hang on for ghostwalker's always superior explanation.
    :blush:

    (Original post by maggiehodgson)
    What am I not doing properly, please?
    You assumed that the top spring would be stretched and the bottom one compressed, which in itself is not a problem - though you have to be more careful thereafter.

    When working out T_2 the extension is "-e_2". If you go with that it will work out correctly.

    It is far easier, as BabyMaths did and I would do, to assume both springs are stretched.
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    (Original post by BabyMaths)
    I'm not sure where you have gone wrong but I would have considered e_1+e_2=1.

    My equation for this problem is \dfrac{100(x-2)}{2}-20(4-x-1)=5g. This leads to the solution you gave. Can you see how I obtained this?

    Hope this helps but if not hang on for ghostwalker's always superior explanation.

    That is so obvious now that you've told me.

    Thank you.
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    (Original post by ghostwalker)
    :blush:



    You assumed that the top spring would be stretched and the bottom one compressed, which in itself is not a problem - though you have to be more careful thereafter.

    When working out T_2 the extension is "-e_2". If you go with that it will work out correctly.

    It is far easier, as BabyMaths did and I would do, to assume both springs are stretched.
    It all makes sense. I will remember that for future.

    If I did it my way, MB compressed, I'm thinking then T2 would be Thrust not Tension so T1+T2 = 5g? I'll give that a go and see if it's true.

    However, I'll redo my drawing and do it the obvious way for my notes.

    Thanks.
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    (Original post by maggiehodgson)
    If I did it my way, MB compressed, I'm thinking then T2 would be Thrust not Tension so T1+T2 = 5g? I'll give that a go and see if it's true.
    Yep, that's another way to deal with it.
 
 
 
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