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Math Help - Quick Physics torque question - Need a check

  1. #1
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    Quick Physics torque question - Need a check

    So I've gotten an answer, but my percent error was huge, which is why I want to make sure that I did it right. Can someone do this real quick and tell me what they get?


    [not drawn to scale]

    Thanks!
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  2. #2
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    net torque caused by the 10 gram mass ?

    (.010)(9.8)(.48) = .047 N-m

    I get x = 2.4 cm to balance the system using the 200 gram mass.
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  3. #3
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    Thanks, that's what I got. I guess it's meant to have a huge percent error. What could be the cause of a 70% error? (the "actual" value should have been 8m with a 200 kg mass)
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  4. #4
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    Quote Originally Posted by Intrusion View Post
    So I've gotten an answer, but my percent error was huge, which is why I want to make sure that I did it right. Can someone do this real quick and tell me what they get?


    [not drawn to scale]

    Thanks!
    M_1 = F_1 \times d_1 = 0.48m \times 0.01(9.81) = 0.047Nm

     \Sigma M = M_1+M_2 = 0.047-(x\times 0.2 \times 9.81) = 0

    Hence:

     x = \frac{0.047}{0.2\times 9.81} = 0.024m
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  5. #5
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    Since 200 is 10 x 20

    It stands to reason that 48/20 = x

    Thus 2.4 cm



    EDIT ---------------------------------

    I see it's already been answered, sorry for excessive posting.
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  6. #6
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    Quote Originally Posted by Intrusion View Post
    Thanks, that's what I got. I guess it's meant to have a huge percent error. What could be the cause of a 70% error? (the "actual" value should have been 8m with a 200 kg mass)
    But it isn't a 200kg mass, it's a 200g mass. 8m is ridiculous compared to the tiny torque exerted by the 10g mass.
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  7. #7
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    Quote Originally Posted by Mush View Post
    But it isn't a 200kg mass, it's a 200g mass. 8m is ridiculous compared to the tiny torque exerted by the 10g mass.
    Yeah, I meant a 200g mass, not kg.
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  8. #8
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    Quote Originally Posted by Intrusion View Post
    Yeah, I meant a 200g mass, not kg.
    Even at that, 8m would produce far too much torque.

    10g mass is placed 48cm away, to balance this a 200g mass would be a lot closer than 48cm... and as you know 8m is far from being closer than 48cm.
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  9. #9
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    Alright, I'll have to enlighten my teacher then and let him know his "actual" answer is wrong. Thanks!
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