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Mechanics problem

  1. Jan 22, 2009 #1
    1. The problem statement, all variables and given/known data
    a man has fallen into a ditch of width d.he is pulled by two of his friends who are on either side of the ditch.the friends pull the man using a rope which is joined to the man and the two pulleys.find the force acting on the man when he is at a depth h inside the ditch.

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Jan 22, 2009 #2
    Hi Quantum, well before anyone suggests any solutions to this problem you should try and have a go at solving this yourself then once you have tried, if you havnt got the correct answer then people can give you some assistance. I would suggest go away and draw down on a diagram the situtation. Things that you need to consider are:

    The man in the ditch:
    - His weight (mg)
    - his depth into the ditch
    - his position horizontaly in the ditch, is he right in the center or is this also variable as the question doesnt specify
    - also is this rope supposed to be one long rope, looped though a hole on the mans clothes somewhere or are they two seperate ropes as it may make a difference in certain situations

    The rope:
    - if you werent aware, the rope can be modeled as having a tension, in the cases of this question we can model the tensions in the rope(s) directed away from the man.

    note that that list may not be a complete list of all the things you have to consider, but most should be there, and it depends on how sophisticated you want to make the model of this scenario.

    I think also you need to clarify what the question is asking, as if you wanted to know the net force acting on the man at a depth d, then one could argue that the net force acting on him is 0N as he may not be moving up. So have a think about that, really try to come up with a solution yourself, clarify the question if only so that you know what your actually trying to find out, then if you really cant get it, tell us what you have attempted and we will be more than happy to help you further :D as the aim here is not to tell you the answer, but to help you reach an understanding about how to get the answer ;-)
    Last edited: Jan 22, 2009
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