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Rope in tug of war

  1. Apr 25, 2008 #1
    1. The problem statement, all variables and given/known data
    In a tug of war two boys exert an equal force of 30N. What is the nett force on the rope?

    2. Relevant equations

    3. The attempt at a solution
    Since there is a tensile force on the rope will it be 30 N?

    (When a spring replaces the rope it will elongate by 'x'. So the force will be kx
    where k is the spring constant)
  2. jcsd
  3. Apr 25, 2008 #2
    The net force on the rope is calculated by summing the forces on it. Remember though, force is a vector (it has direction).
  4. Apr 25, 2008 #3


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    Staff Emeritus
    Science Advisor

    Be careful. Understand exactly what astrorob said: there are two boys pulling on the rope with equal "force"- but in opposite directions. What will the net force on the rope be? Another way of looking at is this: F= ma. What is the 'acceleration' of this rope? So what is the net force on it?
  5. Apr 25, 2008 #4
    sorry to interject, but if it said find the total tension what would that be?
  6. Apr 25, 2008 #5

    Doc Al

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    Staff: Mentor

    It would be meaningless. :wink: Asking for the tension in the rope makes sense, but "total" tension would not. A tension is created by two forces pulling in opposite directions.
  7. Apr 25, 2008 #6
    so would the tension be 60N?
  8. Apr 25, 2008 #7

    Doc Al

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    Staff: Mentor

    No, just 30 N. To create a tension of 30 N requires the ends to be pulled apart by 30 N forces. The tension force is just the force that the rope exerts which must be equal and opposite to the forces that the boys exert.
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