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    Name:  Untitled.png
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Size:  982 BytesAB is a uniform rod of length 5m and weighs 20N. Find the magnitudes of C and D

    I got 8N for D and 12N for C but apparently the answer is 8.6N and 12.4N

    I did:
    (1x20) = (2.5xd) so d = 8 and then I did 20-8 to get 12. What did I do wrong? thank you
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    (Original post by physicshelpme)
    Name:  Untitled.png
Views: 212
Size:  982 BytesAB is a uniform rod of length 5m and weighs 20N. Find the magnitudes of C and D

    I got 8N for D and 12N for C but apparently the answer is 8.6N and 12.4N

    I did:
    (1x20) = (2.5xd) so d = 8 and then I did 20-8 to get 12. What did I do wrong? thank you
    Your answers look fine
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    (Original post by TenOfThem)
    Your answers look fine
    So do you think the answer in the back of the book is wrong??
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    (Original post by physicshelpme)
    So do you think the answer in the back of the book is wrong??
    If there is nothing more to the question than that diagram
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    (Original post by TenOfThem)
    If there is nothing more to the question than that diagram
    Nope, the full question is 'AB is a uniform rod of length 5m and weight 20N. In these diagrams AB is resting in a horizontal position on supports at C and D. In each case, find the magnitudes of the reactions at C and D' and then the diargram
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    (Original post by physicshelpme)
    Nope, the full question is 'AB is a uniform rod of length 5m and weight 20N. In these diagrams AB is resting in a horizontal position on supports at C and D. In each case, find the magnitudes of the reactions at C and D' and then the diargram
    Your book seems to think that 8.6 + 12.4 = 20, which should start alarm bells ringing!
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    (Original post by davros)
    Your book seems to think that 8.6 + 12.4 = 20, which should start alarm bells ringing!
    Good point

    If the weight were 21N then their answers would be correct as 21/2.5 = 8.4
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    (Original post by davros)
    Your book seems to think that 8.6 + 12.4 = 20, which should start alarm bells ringing!
    Weird. I've looked over this question like 5 times in the past hour, wondering how they got those numbers, and until you pointed it out I too legitimately thought that 8.6+12.4 was equal to 20! :eek:
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    (Original post by aznkid66)
    Weird. I've looked over this question like 5 times in the past hour, wondering how they got those numbers, and until you pointed it out I too legitimately thought that 8.6+12.4 was equal to 20! :eek:
    Easily done! I started typing my previous post then went back to re-check my mental arithmetic in case I was about to make an idiot of myself

    It's always worth a quick sanity check with these questions, especially if you suspect the book of having misprints.
 
 
 
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