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How is tension pulling at both ends? Please explain either theoretically or by intuition. Ideally, answers would imagine the string as made of particles, and consider their free-body diagrams to conclude that tension is pulling on both sides.

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Internal forces or stresses on a rigid structure have equal and opposite force vectors between internal segments of an object. So when you chop it into two new FBD, at every new division there is an equal and opposite arrow on each side of the division for the two new FBDs.

So if you apply a force at one or both ends you can just work your way down the rope progressively chopping things up, with the last division being that between the end of the rope and the object it is anchored to, which exposes that internal force.

If the internal forces weren't equal and opposite, then you don't t have a single rigid structure anymore moving as one. It has broken into independently moving pieces.

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  • $\begingroup$ I get why internal forces are zero,but still did not get why tension is pulling at both ends $\endgroup$
    – Gaurav
    May 6 at 3:20
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    $\begingroup$ Because if you work your way down the rope that is the result.The last division between the far end of the rope and what it is tied to will have an vector for the FBD for the far end of the rope that is equal and opposite the other end. $\endgroup$
    – DKNguyen
    May 6 at 3:23
  • $\begingroup$ You mean only the last chopped particle will exert tension force on ceiling and box and tension force is never on rope but instead on objects to which it is tied? $\endgroup$
    – Gaurav
    May 6 at 3:25
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    $\begingroup$ It's on both. Because equal and opposite. The tensioned rope tied to the fixed anchor is another rigid body. It's still an internal force but you have decided to treat the rope and anchor as different. You're just cutting up internal forces. The anchor exerts a pulling force on the rope to the right and the rope exerts a pulling force on the anchor to the left. $\endgroup$
    – DKNguyen
    May 6 at 3:26
  • $\begingroup$ To add, that is also why there is no net movement along the rope itself. When you pull something and even if it moves, you and the object both experience a force, which is why you are struggling to pull it and also why, the object itself is being pulled $\endgroup$
    – Natru
    May 6 at 4:07
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Tension in a string is always pulling however tension in a rod can be pulling as well as pushing.

Tension in a string is always pulling because as soon as it tries to push , by Netwon's 3rd Law it will become slack

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  • $\begingroup$ Appreciate it, but I want some answer by imagining string as made of particles and then by their fbd the conclusion that tension is pulling on both sides $\endgroup$
    – Gaurav
    May 6 at 2:37
  • $\begingroup$ Welcome to Physics Stack Exchange! Please use the comments only to ask other useful information related to answer or some clarification, not for asking upvotes $\endgroup$
    – Natru
    May 6 at 4:13

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