1. The problem statement, all variables and given/known data An 80 N traffic light is supported at the midpoint of a line between two poles that are 30 m apart. If the light sags a vertical distance of 1 m at the midpoint, what is the tension in the supporting line? A 20 lb picture is hung from a nail so that the supporting cords make an angle of 60. what is the tension of each cord segment? Here is the actual homework problem i have to solve: An 80 N picture is hung from a nail as indicated. Assume the zeros in the 80 N weight are significant. The angle between the cords in 78 degrees. What is the tension in the each cord? 2. Relevant equations I am lost here. 3. The attempt at a solution And lost here. There are 2 examples in my instructor's lecture notes that he sends to us by mail that has a street light and another picture hanging from 2 cords. in the street light problem, the tensions are all positive: Tax = TaCosdegree Tay = TaSindegree Tbx = TbCosdegree Tby = TbSindegree and so on. But in the picture problem, some of the equations have a negative out front. such as: Tbx = TbCos60 Tby = TbSin60 Tax = -TaCos60 Tay = TaSin60. why is that? why would some problems be all positive and some get negatives in others? I have realized that i am suppose to set EFx = 0. where the E is the sigma symbol which i believe stands for equilibrium or net. and i am suppose to set EFy = 0. can someone please help me understand this? my instructor has been out sick since last monday with swine flu and he has not returned to work yet.