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Homework Help: A man sits in a seat that is suspended from a rope (tension & force)

  1. Feb 6, 2012 #1
    1. The problem statement, all variables and given/known data
    the rope passes over a pulley suspended from the ceiling, and the man holds the other end of the rope in his hands. What is the tension in the rope and what is the force supported by the pulley.

    2. Relevant equations
    3 theories of newton

    3. The attempt at a solution
    since its in equilibrium i guess that the force in the pulley is zero. the tension in the rope at the top is the weight of the person + chair and the weight of the rope.
  2. jcsd
  3. Feb 6, 2012 #2


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    Hello chaotiiic. Welcome to PF !

    Is there any more information that goes with this question? --- like weight or mass of the man and/or the seat ?

    According to the rules of this Forum: https://www.physicsforums.com/showthread.php?t=414380
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    On helping with questions: Any and all assistance given to homework assignments or textbook style exercises should be given only after the questioner has shown some effort in solving the problem. If no attempt is made then the questioner should be asked to provide one before any assistance is given.​
    So you need to show what you know or what you're thinking about this problem before we can help.

    "idk." is probably not enough.
  4. Feb 6, 2012 #3


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    welcome to pf!

    hi chaotiiic! welcome to pf! :wink:
    yes that's correct (except that we say "the force on the pulley" :wink:)

    (oh, and if you're going to include the weight of the rope, then you should include the weight of the pulley also)

    ok, that was the tension in the rope at the top…

    now what about the tension in the other rope? :smile:
  5. Feb 6, 2012 #4
    @sammy thanks for the welcome. there is no additional info given. its just a written response. no math.

    @tiny the problem doesnt specify which part of rope where i find tension. idk if its at the top on the pulley, tied to the chair, or held by the man's hand. after skimming through my book i guess the tension at the pulley is the weight of the rope + man + chair. the tension at point tied to the chair is just the rope. the tension held by the man's hand is also just the rope. is this right?
  6. Feb 6, 2012 #5


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    yes it does … it asks for the tension in the rope that passes over the pulley (ie up to the pulley, over the top, and down again)
    this doesn't make any sense :redface:

    tension can't be at a point, or in someone's hand

    there is a rope, it has a tension

    do you know what a free-body diagram is? if so, draw one for each of the bodies in the question​
  7. Feb 6, 2012 #6
    my teacher sucks. he gives out quizes before the actual lecture. the good news is that they are take home quizzes. yes i knda know what free body diagrams are because my book showed me a couple examples but we havent done any in class. im just going to put the tension is the ropes weight + man + chair.
  8. Feb 7, 2012 #7


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    hi chaotiiic! :smile:

    (just got up :zzz: …)
    that's no way to learn :redface:

    draw the fee body diagram for the man-and-seat…

    draw all the external forces on that body (how many are there?) …

    now add them up :smile:
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