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Pulling a Thread Attached to Weight

  1. Oct 7, 2004 #1
    Suppose in a scenario a weight is hanging on a string from a rod. There is a second string at the end of the weight:

    -------|---thread 2

    Now suppose a person's hand pulls on the bottom string.

    How would the force diagram be drawn? There is a force of tension above the weight, but what about the others forces (like the 1 below the weight)? What is going on? Please help with the other force(s).

  2. jcsd
  3. Oct 7, 2004 #2


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    You're looking for a force diagram for the weight? Well, think about it: the string above the weight is pulling upward. The string below the weight is pulling downward. And there is one more downward force on the weight, but that one should be obvious.

    I suppose you're worried about the force of the person's hand? Well, that person isn't pulling on the weight, is he? He's pulling on the string.
  4. Oct 7, 2004 #3
    There is a tension force say T1 in thread one. T1 acts upwards on the weight while its weight force acts down. There is a tension T2 in the thread 2. T2 acts downwards on the mass (incidentally, T2 is the applied force). So the mass is being acted upon by the following forces:

    T1 upwards
    T2 downwards
    W (its weight) downwards.

    Hope that helps. Now please go ahead and draw a freebody diagram to understand this. When in doubt, draw a diagram and consider your system sectionwise accounting for all the forces that you can think of.

  5. Oct 8, 2004 #4
    So is F_t2 - F_t1 + mg = ma correct?

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