Hi. I recently started learning physics on my own, and I'm having a bit of a problem with the concept of tension. That is, I'm not exactly sure what it is. In the textbook I bought, tension is defined a bit hastility in a section entitled "Applications of Newton's Laws." I grasped the Three Laws very well, but the defintion of tension has me questioning a lot. The formal defintion of tension is as follows: I'm not really sure what to make of this. I understand that if I pull the rope with a force of 100 N, the box will also have a pull of 100 N. However, because of Newton's Third Law, there is will be a 100 N force pulling on the right end of the rope because of me, and there will be a 100 N force pulling to the left of the rope because of the box. Wouldn't this mean the tension is 200 N? I generally think of tension as stretching, and viewing the tension as 100 N seems a bit like one-sided stretching, which doesn't make sense. If someone has an explantion of tension that might shed some light on my current concept, I'd be really grateful if you shared it. As it is now, I'm stuck on an Atwood Machine problem because I'm unsure about the whole tension business. NOTE: To give you an idea of my level, the questions I'm working on all neglect mass and say that the magnitude of the force exerted at any point along a rope is the same at all points on the rope.