I'm going to provide my argument for why I think the tension in a rope should be twice the force exerted on either side of it.
First, let's consider a different example.
Say, there is a person named
A and a block in space.
A pushes on the block with a force of 100 N. Then, the block will also push
A with a force of 100 N by Newton's third law.
Now, consider the case where instead of the block, there is a person
B who is also pushing on
A with a force of 100 N while
A is pushing on him.
A will experience a force of 100 N because he pushed on
B, AND another 100 N because he is being pushed by
B. Hence he will experience a force of 200 N. Similarly,
B also experiences 200 N of force.
Now, back to the original problem.
There are two people
B in space with a taut rope (no tension currently) in between them. If only
A is pulling and
B is not, then I agree that the tension is equal to the force
A exerts. This situation (in my opinion) becomes analogous to the above if
B is also pulling. So, say both of them pull from either side with a force of 100 N. Then the rope at the end of
B will pull
B with a force of 100 N (this pull is caused by
A). By Newton's third law, the rope will experience a pull of 100 N. But
B is also pulling his end of the rope with 100 N. Therefore, the tension should be 200 N. Similarly, the end of the rope at
A must pull
A with 100 N of force (because
B is pulling from the other side) and hence experience a force of 100 N itself by Newton's third law plus another 100 N because
A is pulling on the rope.
Apparently, the answer is not this (according to my searching on the web). So, could anyone tell me why this reasoning is wrong? Thanks.
EDIT : So apparently people don't agree with my first example, leave alone the second.
This is to the downvoters and the upvoters of the highest-rated answer: You all agree that if only
B with a force of 100 N, then
B both will get pushed by a force of 100 N in opposite directions, right? Then, in the case where
B is also pushing with a force of 100 N, it doesn't make sense that the answer would be exactly the same. It doesn't seem right that no matter what
A will always experience the same force as they would have if
B hadn't applied any force.
EDIT 2 : I'm going to provide here a link to a question that I posted: Two people pushing off each other According to the answer and the comments there, the reason as to why my first example is incorrect is different to the one provided here. So maybe you should all read the answer and the comments provided by the person and reconsider what you think.