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Forces on each end of a breaking rope

  1. Feb 15, 2012 #1

    J77

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    Long time no post but the following came up in a recent coffee time discussion:

    If you pull on a rope which is fixed to, say, a wall, and the rope breaks, what are the forces on each end of the rope.

    (We can assume the rope has some elasticity.)

    Putting it in other words, in equilibrium the inward tension forces on the rope would balance and these in turn would balance the pulling force and the reaction force in the wall. However, when the rope snaps/breaks does one measure more of the (resultant) equilibrium force in the free end (or in the wall) depending on where the rope breaks; ie. if it breaks nearer the wall or the free end...?

    I've even searched academic literature but can find no answer...
     
  2. jcsd
  3. Feb 15, 2012 #2
    Hi, I'm just a first year student but I think I have an input.
    The forces would still be in equilibrium as I assume that the wall could match a reaction force much greater than the force it takes for the rope to snap as I believe rope is a brittle material. Sorry if I'm completely wrong, just giving my two cents.
     
  4. Feb 15, 2012 #3

    J77

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    I was thinking something along the lines of: when the (elastic) rope is tensioned it stores energy in a spring-like way; when the rope snaps the energy is released; however, the rope does not snap in the middle and therefore you have release of energy in 2 effective different lengths of rope (springs) -- how does this effect the forces...?
     
  5. Feb 15, 2012 #4
    How about this? since the rope is assumed to have certain elasticity therefore the internal forces will balance each other for a certain degree but if this ratio is disrupted i.e. a greater amount of tensile force is applied which could not be overcome by internal balancing of forces then the rope undergoes deformation as a result it breaks. Sorry if I am wrong:)
     
  6. Feb 15, 2012 #5
    After many years in the lifting & rigging industry, having installed load cells thousands of times to measure the load, I can affirm that it works just like you were taught in your Statics class. Load is the same at both ends. Any difference is caused by friction in pullies or the weight of the rope.
     
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