I am trying to figure out how tension works. It is not intuitive to me. I know tension means the stretch on a string that opposes some force. But what happens when forces pull on either side?   -20N <--------------string-------------------> 20N   Is the total tension 20N, 40N, or 80N, and why? I would think it is 0N of tension so that there's no net force on the string, but that's just ridiculus.