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Math Help - [SOLVED] Torque Problem

  1. #1
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    Question [SOLVED] Torque Problem

    Hello, the question I'm trying to complete states: A wrench 0.1 meters long lies along the positive y-axis, and grips a bolt at the origin. A force is applied in the direction of at the end of the wrench. Find the magnitude of the force in newtons needed to supply 100 newton-meters of torque to the bolt.
    So far I know, r=.1m, \tau=100Nm \ and \ |\tau|=|r \times F|=|r||f|\sin\theta
    So I need to find F right? But why does the problem give me a force already? Do I have this problem set up correctly?

    Thanks,
    Matt
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  2. #2
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    anybody? this problem is making me go lol
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  3. #3
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    Quote Originally Posted by matt3D View Post
    Hello, the question I'm trying to complete states: A wrench 0.1 meters long lies along the positive y-axis, and grips a bolt at the origin. A force is applied in the direction of at the end of the wrench. Find the magnitude of the force in newtons needed to supply 100 newton-meters of torque to the bolt.
    So far I know, r=.1m, \tau=100Nm \ and \ |\tau|=|r \times F|=|r||f|\sin\theta
    So I need to find F right? But why does the problem give me a force already?
    it didn't ... it gave you a torque


    \vec{r} = <0,0.1,0>
    \vec{F} = <0,-5F,-4F>

    \vec{\tau} = \vec{r} \times \vec{F} = -0.4F \vec{i}

    0.4F = 100 Nm

    F = 250 N
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  4. #4
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    Quote Originally Posted by skeeter View Post
    \vec{r} = <0,0.1,0>
    \vec{F} = <0,-5F,-4F>

    \vec{\tau} = \vec{r} \times \vec{F} = -0.4F \vec{i}

    0.4F = 100 Nm

    F = 250 N
    Thank you skeeter. That makes sense. I put in 250N but the answer was still incorrect, but once I realized it wanted the magnitude, I just plugged in 250 to the direction of the force took it's magnitude and got 1600.78N and it was correct. Thanks again!
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