Timeline for Why I think tension should be twice the force in a tug of war
Current License: CC BY-SA 4.0
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| S Oct 10 at 15:05 | history | suggested | Bml | CC BY-SA 4.0 |
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| Oct 14, 2020 at 16:31 | comment | added | Adrian Howard | When you pull with 100N and the other person pulls with 100N, if that would add to 200N tension on the rope do you think that would mean that if you pulled on the rope with no one on the other end the tension would be 100N? | |
| Dec 5, 2019 at 13:01 | answer | added | Robert DiGiovanni | timeline score: 0 | |
| Dec 5, 2019 at 12:22 | answer | added | Professor Sushing | timeline score: 1 | |
| Dec 5, 2019 at 9:53 | history | edited | Qmechanic♦ |
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| Jul 13, 2019 at 8:38 | answer | added | Adrian Howard | timeline score: 1 | |
| Mar 1, 2018 at 22:04 | comment | added | bruno | @Alraxite just to keep you updated I edited my answer to explain why to consider the tension on the cable to be 100N even though thinking of 200N wouldn't be unreasonable. | |
| Feb 24, 2018 at 8:44 | answer | added | bruno | timeline score: 1 | |
| Apr 13, 2017 at 12:40 | history | edited | CommunityBot |
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| Mar 15, 2015 at 18:48 | comment | added | Žarko Tomičić | To add a comment...lets forget all about rope and just pull the mass M with some acceleration so that it adds up to 100 N. If you are pulling it with 100 N it pulls back with 100 N. If you are doing it with the spring, it will show 100 N. Rope or wall, same thing. | |
| S Aug 13, 2014 at 0:48 | history | bounty ended | DLV | ||
| S Aug 13, 2014 at 0:48 | history | notice removed | DLV | ||
| Aug 7, 2014 at 6:20 | answer | added | abalter | timeline score: 7 | |
| Aug 6, 2014 at 19:08 | answer | added | Floris | timeline score: 28 | |
| Aug 6, 2014 at 18:00 | comment | added | rmhleo | @Alaxrite: Do follow @(Jerry Schirmer) sugestion! In physics this always yields the truth, and is otherwise hard to understand where your misconception arises. But in your 1st example, the block force on A is equivalent to the force of B on A. As with the block, if A and B push each other with the same force, none will move (or both will move equally if the floor is slippery). And if they do move and their masses are different, their movements reflect the inverse proportion. Both block and B forces are as big as their opposition to movement can be, and this is the force that A feels. | |
| Aug 6, 2014 at 4:05 | history | tweeted | twitter.com/#!/StackPhysics/status/496869730570227713 | ||
| S Aug 6, 2014 at 3:25 | history | bounty started | DLV | ||
| S Aug 6, 2014 at 3:25 | history | notice added | DLV | Canonical answer required | |
| Jul 24, 2014 at 18:24 | history | protected | Qmechanic♦ | ||
| Jul 24, 2014 at 18:23 | answer | added | Tim B | timeline score: 0 | |
| Jun 28, 2013 at 0:59 | answer | added | islyika | timeline score: -3 | |
| Oct 31, 2012 at 10:56 | history | edited | Alraxite | CC BY-SA 3.0 |
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| Oct 31, 2012 at 10:38 | history | edited | Alraxite | CC BY-SA 3.0 |
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| Oct 31, 2012 at 5:37 | history | edited | Alraxite | CC BY-SA 3.0 |
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| Oct 31, 2012 at 4:48 | history | edited | Alraxite | CC BY-SA 3.0 |
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| Oct 21, 2012 at 14:09 | history | edited | Alraxite | CC BY-SA 3.0 |
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| Oct 21, 2012 at 13:51 | history | edited | Alraxite | CC BY-SA 3.0 |
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| Oct 21, 2012 at 10:01 | comment | added | David Z | By the way, downvoters are of course entitled to their opinion, but I do think this is a good question because it asks about a conceptual problem, and a somewhat subtle one at that. The fact that it's based on a misconception is not a problem IMO, and in fact such questions often turn out to prompt insightful answers. | |
| Oct 20, 2012 at 21:01 | comment | added | dmckee --- ex-moderator kitten | A number of comments that were contributing to personalizing the discussion deleted. | |
| Oct 20, 2012 at 19:08 | comment | added | Zo the Relativist | @Alraxite: you have the block, person A and person B. Or the rope, person A and person B. As for your tension example, if you pull a rope and move it with no one pulling back on the other end, the tension will be zero. Pick up a string or an extension cord and do it yourself. It will flip about all floppy-like. No tension. In both cases, person A does not feel force from person B. Person A feels a force from the rope, ONLY. | |
| Oct 20, 2012 at 19:06 | comment | added | Alraxite | @JerrySchirmer I hope my examples aren't ambiguous but in all these examples, there are only two objects or people. So I'm not sure where you are coming from. | |
| Oct 20, 2012 at 18:27 | comment | added | Zo the Relativist | @Alaxrite: I suggest you get two spring scales and a rope and perform this experiment yourself. Your example is wrong. The action/reaction pair of A and the block has nothing to do with what B is doing. You can make this really clear by drawing free body diagrams for the three objects. | |
| Oct 20, 2012 at 18:19 | history | edited | John Alexiou | CC BY-SA 3.0 |
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| Oct 20, 2012 at 17:41 | history | edited | Alraxite | CC BY-SA 3.0 |
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| Oct 20, 2012 at 16:53 | answer | added | Emilio Pisanty | timeline score: 5 | |
| Oct 20, 2012 at 16:23 | history | edited | Alraxite | CC BY-SA 3.0 |
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| Oct 20, 2012 at 15:22 | comment | added | Alraxite | @miceterminator That would happen if the mass-less rope isn't attached to anything. But it is, and it is attached to 'B' which has mass and hence it provides a reaction force by the third law. | |
| Oct 20, 2012 at 15:09 | comment | added | miceterminator | Sorry I didn't read through your whole text. "If only 'A' is pulling and 'B' is not, then I agree that the tension is equal to the force 'A' exerts." This does not work if you pull a massless rope with 100N there is no tension It would just accelerate infinitely. | |
| Oct 20, 2012 at 15:08 | answer | added | Ignacio Vazquez-Abrams | timeline score: 11 | |
| Oct 20, 2012 at 14:58 | comment | added | Alraxite | Yes, but that's because only one side is doing the pulling. The block is being pulled by gravity downwards and since it is not moving it must be the case that the rope is pulling upwards with a force equal to its weight which implies by Newton's third law that the block is pulling downwards on the rope with the same force. Similarly, at the other end, the rope pulls the ceiling with a force equal to the weight of the block and hence again by the third law, the ceiling pulls the rope with the same force. So I see no reason to say that the tension would be twice the weight. | |
| Oct 20, 2012 at 14:42 | comment | added | miceterminator | Imagine 1Kg-block hanging on the ceiling. Each hook (the one in the ceiling and the one in the 1Kg-block) pull with 100N still you would not get the Idea that the tension would be 200N. In the rope example the ground takes care of the other 100N. | |
| Oct 20, 2012 at 14:29 | history | edited | Alraxite | CC BY-SA 3.0 |
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| Oct 20, 2012 at 14:24 | history | asked | Alraxite | CC BY-SA 3.0 |