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Homework Help: Tension, horizontal & vertical tension

  1. Jul 17, 2009 #1
    1. The problem statement, all variables and given/known data

    A mass Z is suspended by a vertical rope attached to the roof, and a second rope attached horizontally to a wall.

    what is the tension in each rope if Z is hanging straight down?

    What are the rope tensions?

    Suppose Z has a mass of 800kg. what is the tension in the pair of ropes?

    These questions have me stumped!
    ANy help appreciated!
    Last edited: Jul 17, 2009
  2. jcsd
  3. Jul 17, 2009 #2


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    I'd start by drawing a free body diagram, or posting the diagram if one is give.

    Also what does this mean?

  4. Jul 17, 2009 #3
    Sorry, I stuffed it up. fixed.

    I have drawn a basic diagram but just do not know the formulas etc

  5. Jul 17, 2009 #4


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    Post your diagram.

    (Upload it to http://imageshack.us" [Broken] and copy & paste one of the forum board URLs)
    Last edited by a moderator: May 4, 2017
  6. Jul 17, 2009 #5
    http://img529.imageshack.us/img529/6206/98546679.png [Broken]

    Sorry, its just a quick mockup in paint of what I have on paper.
    Last edited by a moderator: May 4, 2017
  7. Jul 17, 2009 #6


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    uhm what are those things in green?
  8. Jul 17, 2009 #7
    Vectors? - Gravity, equilibrium, constructed vectors for the ropes?

    Am i wayyyy off track?
  9. Jul 17, 2009 #8


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    Well normally if it is hanging straight down, I don't see the point in the second horizontal rope. But given the problem, I can only tell you to draw in the forces acting and then use the fact that it is in equilibrium to get the tensions.
  10. Jul 17, 2009 #9
    This is the bit I am having trouble with.
    So the forces acting would be gravity pulling Z down, which needs an equal and opposite vector for equilibrium (upward). the vector of the diagonal of the parallelogram?

    Its got me royally stumped.
  11. Jul 17, 2009 #10


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    Well if you remove all the green for the moment, you just have the ropes and the mass.

    Now acting on the mass (vertically), there is tension and weight (you know that acts downwards). So what direction should the tension act in this rope?

    Similarly, horizontally, there is only tension acting.
  12. Jul 17, 2009 #11
    Vertically the direction of the tension in the rope should be upward.
    Horizontally the tension in the rope should be acting toward the wall?
  13. Jul 17, 2009 #12


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    Yes that is correct. So if vertically the mass does not move, what is the resultant force in the vertical direction? (Do the same horizontally)
  14. Jul 17, 2009 #13
    So the tension on the vertical rope is 9.8N? same for the horizontal?
  15. Jul 17, 2009 #14
    i'm confused with the horizontal one

    i think there is only one force on horizontal direction which is tension towards the wall.
    if so, then the system isn't in equilibrium
  16. Jul 17, 2009 #15
    Precisely why the horizontal force is zero =)
  17. Jul 17, 2009 #16
    oh, i see

    but in fact i think it's possible to construct such system. I hang the mass and add a horizontal string which has a certain value of tension
  18. Jul 17, 2009 #17


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    The horizontal string won't have any tension value unless you intentionally tighten it up and induce a value in it, in which case the mass and the upper rope will swing in toward the wall at a certain angle, but that's a different problem.
  19. Jul 17, 2009 #18
    Well yes, you can add the horizontal string, but if the mass is hanging vertically downwards, that must mean the horizontal string isn't taut.
  20. Jul 17, 2009 #19
    thanks for the explanation ^^
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