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Homework Help: Physics Tension question

  1. Jun 8, 2015 #1
    1. The problem statement, all variables and given/known data
    I am just doing problems in 3000 solved physics problems in physics and I disagree with one of the answers and wanted to see if I am just an idiot or not

    This is the picture of the problem

    This the a picture of the solution in the book. It maybe hard to see the answers, but they say the tension in T5 should be 651N, this is what I disagree with.

    3. The attempt at a solution

    So they say that T5 is 651N, but I think it should be 1302N because technically you have 651N pulling the 5th wire to the left and 651N of force pulling the wire to the right. Am I incorrect about this?

    Thanks for reading
  2. jcsd
  3. Jun 8, 2015 #2


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    Yes, you are incorrect. The tension is the force across a cross section of a wire. If you make a free body diagram of any part of the wire, the force across a section of the wire is the tension T5. If he wire is being pulled from one direction with 651 N, then this is the force across a section of the wire, and therefore the tension.

    Also, please post your work in more detail in the future and make sure your images are more readable. You should also write out the problem in text. See the link to the homework guidelines in my signature.
  4. Jun 8, 2015 #3


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    Yes, you are incorrect. This is a common misunderstanding about tension.

    Consider, for instance, a wire attached to a hook on a wall. You pull the free end of the wire with a force of 651N so that the wire is taut. How much tension is the wire under? How much force is the wire exerting on the wall? How much force is the wall exerting on the wire?
  5. Jun 8, 2015 #4
    Ahh I see now. Thanks for quick response guys that really helped me out. Sorry for incorrect format, I'll make sure to do it correctly next time.
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