Rope in tug of war

  • Thread starter timseb
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  • #1
timseb
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Homework Statement


In a tug of war two boys exert an equal force of 30N. What is the nett force on the rope?


Homework Equations





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)
 

Answers and Replies

  • #2
astrorob
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The net force on the rope is calculated by summing the forces on it. Remember though, force is a vector (it has direction).
 
  • #3
HallsofIvy
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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?
 
  • #4
Sheneron
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sorry to interject, but if it said find the total tension what would that be?
 
  • #5
Doc Al
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sorry to interject, but if it said find the total tension what would that be?
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.
 
  • #6
Sheneron
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so would the tension be 60N?
 
  • #7
Doc Al
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so would the tension be 60N?
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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