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Homework Help: Torque Tension

  1. Oct 30, 2006 #1
    A 2-m long uniform rod AB is suspended horizontal by two vertical strings attached to the ends A and B. The rod has a mass of .6kg. A mass of 2kg suspended from the rod .8m from the end A. Determine the Tension in each string.

    Hi, I have a physics worksheet I am trying to work on. This has confused me, I'm unsure of what to put inside of the equation without any angles and two different strings. I have labeled A T1 and B T2 and I know T1>T2. Also Torque must = 0 for the system to be in equilibrium so I make an equation = to T0 but if anyone could help with what to put into the equation I need some help. Thanks so much!
     
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  3. Oct 30, 2006 #2

    radou

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    What to put in the equation? Well, torques, for example. :smile: If you know the definition of a torque, there shouldn't be any problems.
     
  4. Oct 30, 2006 #3
    Right, but which masses? Is it something like Torque0 = T1(2.6)(.8) - T2(1)(.6)? Are they subtracted or added?
     
  5. Oct 30, 2006 #4

    radou

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    You can start by calculating setting the torque with respect to point A (or B) equal to zero. If the torque 'rotates' clockwise, choose a positive sign, and if it 'rotates' counter clockwise, choose a negative sign.
     
  6. Oct 30, 2006 #5
    Its not rotating either way, the whole beam is in equilibrium. The two strings are holding it up and I need their tensions.
     
  7. Oct 30, 2006 #6

    radou

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    I know it's not rotating, I didn't mean that literarely. I was talking about the direction of the torque.
     
  8. Oct 30, 2006 #7
    What are the tensions notwithstanding the 2 kg mass? What does the 2 kg mass add to the downward force of each end of the bar? How does this influence each tension?
     
  9. Oct 30, 2006 #8
    It would cause a downward counter clockwise motion that is positive. The tension is greater for the string on A than B w/ more weight. The weights need to be converted to newtons and multiplied by 9.81 for gravity.
     
  10. Oct 30, 2006 #9
    What is the effect of the added mass on each string?
     
  11. Oct 31, 2006 #10

    radou

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    As said before, use the equations of equilibrium. How is equilibrium expressed? What must vanish? You can use two torque equations (with respect to points A and B), and use the fact that the sum of the vertical forces must vanish as a check.
     
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