Torque Tension

  • Thread starter catenn
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  • #1
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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!
 

Answers and Replies

  • #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.
 
  • #3
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Right, but which masses? Is it something like Torque0 = T1(2.6)(.8) - T2(1)(.6)? Are they subtracted or added?
 
  • #4
radou
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catenn said:
Right, but which masses? Is it something like Torque0 = T1(2.6)(.8) - T2(1)(.6)? Are they subtracted or added?

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.
 
  • #5
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Its not rotating either way, the whole beam is in equilibrium. The two strings are holding it up and I need their tensions.
 
  • #6
radou
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catenn said:
Its not rotating either way, the whole beam is in equilibrium. The two strings are holding it up and I need their tensions.

I know it's not rotating, I didn't mean that literarely. I was talking about the direction of the torque.
 
  • #7
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catenn said:
Its not rotating either way, the whole beam is in equilibrium. The two strings are holding it up and I need their tensions.
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?
 
  • #8
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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.
 
  • #9
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catenn said:
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.
What is the effect of the added mass on each string?
 
  • #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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