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Another Pulley Question

  1. Oct 19, 2005 #1
    A small man is sitting in a bosun chair that dangles from a massless rope, which runs over a massless frictionless pulley and back down to the mans hand. The combined mass of the man and the chair is 95kg. with what force magnitude must the man pull on the rope if he is to rise?

    Mass = 95Kg
    a = ?
    v = ?
    F = ?

    I didnt get very far with this one, I drew one F.B.D for the man and got the following:
    Nothing in the X direction
    y--------T+v = -mg

    Heres a link to a drawing
    http://img438.imageshack.us/img438/8349/pulley27xt.png [Broken]

    Should i draw another F.B.D for the mans hands on the rope?
    Last edited by a moderator: May 2, 2017
  2. jcsd
  3. Oct 19, 2005 #2
    if so would T act up onlong with mg and v act downwards?
  4. Oct 19, 2005 #3
    Hi, the weigh of the man + weigh of the chair is around 950 N.
    When the man pulls hiomself with his hand with a force F, the chair exerts also a force F on him.
    Just to have equilibrium 2F = 950 N so F = 450 N
    With a little push up (say with his feet on the ground) the chair and him will move up at a constant speed if he maintains the constant force 450 N on the rope
    Any force greather than 450 N will cause an acceleration of the man and the chair up in the air.
    I hope it helps you
  5. Oct 19, 2005 #4
    so theres no math involved?
    kinda makes sence since there are 3 unknows..

    2f = 931N
    f = 465.5N

    Also there is more to the question..si are my free body diagrams correct?
    Last edited: Oct 19, 2005
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