The question I am looking at has a man of X kilograms of mass, with a rope tied around his waist. That rope is thrown over a tree limb. The man pulls on the other end of the rope to hoist himself up, with say, Y netwons of force (tension). The aim of the problem is to solve for his acceleration. The answer to this question says that the forces acting upon him are his weight mg, and 2 tension forces upwards. So net force is F = 2T - mg I am racking my brain to understand why the downward force of his hand doesn't contribute to the net force. 1) Is it because this force isn't acting upon the system (AKA the man). Rather, it is a force that the system exerts on another object, and thus, it shouldn't be counted? 2) How do we know that the tension pulling up on the man's waist is pointed upwards? I know that the tension of a rope is the same all along a rope, but does that include direction? 3) Also, I don't understand why weight doesn't contribute to the tension in the rope. I am studying physics for the MCAT and tension gets me every, single time. I need to master it once and for all..Been attempting every and any tension problem I come across lol..