Tension in a string being pulled from both ends

  • #26
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I do not know the reason but I have found in one of my books that when a rope or string is pulled with equal forces on two sides ,tension in the rope is equal to either of the forces applied.Maybe this might be somewhat helpful...
 
  • #27
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I do not know the reason but I have found in one of my books that when a rope or string is pulled by equal forces on opposite sides then the tension is equal to either of the forces. Maybe this might be helpful...
 
  • #28
PeroK
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I do not know the reason but I have found in one of my books that when a rope or string is pulled by equal forces on opposite sides then the tension is equal to either of the forces. Maybe this might be helpful...
If it was only pulled from one end it would move and there would be no tension.
 
  • #29
hy, i have a idea, we take the concept of equilibrium
If we hang a body of some weight with one end on string and other is fixed with something then body is in equilibrium because net force is zero due to tension and weight because by newton third law tension in the string and weight are equal but opposite
so tension is that force which applied by fixed point so tension is a force which are applied through string on any body
so if we pull both end by 60 N then tension is string is also 60 N but total force is zero
 
  • #30
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I understand that the tension is equal to W, but, I do not understand why it equals W as oppose to it equaling 2W. I need to have the explanation of why tension would equal W to get points for corrections on my test.
 
  • #31
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View attachment 109644

I understand that the tension is equal to W, but, I do not understand why it equals W as oppose to it equaling 2W. I need to have the explanation of why tension would equal W to get points for corrections on my test.

If it was ##2W## each mass would have an unbalanced upward force of ##2W - 1W## acting on it and each would acclerate upwards!
 
  • #34
haruspex
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If we do not apply any force on a string than what's the tension?
Why would there be any tension? Perhaps you need to describe the complete set-up you have in mind.
 
  • #35
Why would there be any tension? Perhaps you need to describe the complete set-up you have in mind.
Yes, there is no tension
Tension produced in string due to our applied force so if we hang any things with an inextensible string the tension in the string is equal to weight of that thing but both have different direction
 
  • #36
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both have different direction
What have different direction? Tension has an inward direction, as opposed to the outward direction of a compression. The forces exerted at the two ends of the (straight) string by the tension are in opposite directions. But it doesn't really mean anything to say that a tension is in the opposite direction to a force.
 
  • #37
What have different direction? Tension has an inward direction, as opposed to the outward direction of a compression. The forces exerted at the two ends of the (straight) string by the tension are in opposite directions. But it doesn't really mean anything to say that a tension is in the opposite direction to a force.
Yes, that's my mean
 
  • #39
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But I still don't get this
If the string is being pulled by forces 60 and 70N from either ends then what's the tension
1.On first thought I think tension should be greater than 60N..because earlier in the discussion I saw when the string was being pulled with 60N from either sides tension was 60..now since I increased one of the forces then shouldn't there be greater stretched tendency sort of??? I.e greater tension than 60N???
On second thought
I imagine a situation let there be a mass m , attached to it is an ideal string now apply force F on th side opposite to where the string is stuck directly on the block tension must be 0..you can do the math now when the string is being pulled in opposite direction of F with force f...then tension is f ... again you can do the math I've done it...connecting this to this question I asked let the original force "F" be 70 and "f" be 60 therefore I arrive at tension=60....as you can see I'm utterly confused with my own thought processes . Any help and explanation is greatly appreciated
 
  • #40
haruspex
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If the string is being pulled by forces 60 and 70N from either ends then what's the tension
What would be the net force on the string? What will happen in consequence?
 
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  • #41
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Consider what happens if you subject a string to 1,000,000N in one direction and 0.000,000,1N in the other. What do you think the tension in the string will be?
 
  • #42
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Ok so I have a similar homework problem and I've read the thread but I'm still failing to understand. Sorry if it's dumb and repetitive, but if you had a string on a pulley with two weights on each side, each exerting a force of 80N would the tension on the string be the same throughout? Would the centre of the string have a tension of 0?
 
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  • #43
haruspex
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would the tension on the string be the same throughout?
Yes.
Think of the string as made up of a lot of short segments. Each part pulls on each of its neighbours with the same force.
 
  • #44
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+1

Break the problem into parts and think about the forces that adjacent parts apply on it.
 
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  • #45
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Ok so I have a similar homework problem and I've read the thread but I'm still failing to understand. Sorry if it's dumb and repetitive, but if you had a string on a pulley with two weights on each side, each exerting a force of 80N would the tension on the string be the same throughout? Would the centre of the string have a tension of 0?
I think students often get confused because they have only a nebulous idea of exactly what tension is. When you say the tension in the string is, say, 80 N, it means that the string exerts a force of 80 N on whatever it's attached to.
 
  • #46
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I think students often get confused because they have only a nebulous idea of exactly what tension is. When you say the tension in the string is, say, 80 N, it means that the string exerts a force of 80 N on whatever it's attached to.
NOW I understand! Thank you!
 

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