1. The problem statement, all variables and given/known data There is no one particular problem, but I will give one that I am struggling to understand as an example: A block of mass m = 15.0 kg is hanging from three strings. What are the tensions in the strings? There is a diagram that goes with this problem. There is one string (C) directly connected to the mass and two strings (A, B) connected to the ceiling that meet at the first string (C). String A meets the ceiling at an angle of 30 degrees, string B at 45 degrees. 2. Relevant equations m = 15.0kg 3. The attempt at a solution This is actually an example in the book, so I have the solution in front of me. I understand how the problem is set up, equations, etc. The sole thing I don't understand is why the strings are pulling the directions they are pulling. For instance, why are strings A and B pulling up on C? Don't all three strings have a pull in both directions? Please make this concept of tension clearer for me. The book does a poor job.