There's two questions about tension(the force), that no matter how much I try to find answers to and understand since the past few days, I'm simply not able to. Any help in this matter would be highly appreciated. 1) If person A and person B are holding a rope, and person A applies 100N of force, he would get a reaction of 100N and the tension in the rope would be 100N. Fair enough. Now, if person B pulls with 100N too, person B would be pulled not only by the reaction force of 100N, but also by the force exerted by person B. In this case, shouldn't the tension be = 200N? Related sub-question: If a block of 10 kg is hanging from the ceiling, It would be exerting 100N downwards and get a reaction from the rope of 100N, and the ceiling would pull it with 100N too. So shouldn't the tension be 200N? 2) If person A is pulling the string with 100N and person B with 200N, why is the tension in the rope 100N? I've read somewhere that in a string with negligible mass, this would result in the string slipping off the hands of person A, which makes sense. But why wouldn't that be the case with a string with mass too?