1. The problem statement, all variables and given/known data I spent a few hours trying out this question, so I probably need help. This is a seven pin-jointed structure mounted on the wall, with the following information given: 1) S1 and S2 are wall supports, but S2 is assumed to have no friction with the wall i.e. no vertical support provided to P4 from the wall. 2) The weights W are of the same mass, and in this question is of not much relevance to the answer. 3) The whole system is in static equilibrium, and idealization is assumed. The question requires us to determine if each rod is in compression or tension. 2. Relevant equations Nil. 3. The attempt at a solution After much resolving and equating (which I shall not post here due to lack of space, I have determined the following: 1) Rod P1P3 is in tension. 2) Rod P1P2 is in compression. 3) Rod P2P3 is in compression. 4) Rod P3P5 is in tension. 5) Rod P2P4 is in compression. 6) Rod P2P5 is in tension. 7) There are no forces along P4P5. This is after checking that each point P1 to P4 is in static equilibrium, and that the tension and compression on each rod is equal and in opposite directions. I determined that there is no force along P4P5 as there is no vertical component from the wall, and since the rods are assumed to be massless, there should only be a compressional force acting on P4 to counter the reaction force from the wall. The problem comes when I try to resolve P5. As the tension along rod P3P5 and the reaction force from the wall act in the same direction, I am missing a horizontal component acting towards the wall on P5. But if I made a mistake along P2P5 try to balance out the horizontal component on P5 with compressional force from P2P5, there would be no upward-acting force on P2 to balance the downward-acting forces on P2. Moreover, friction (or some upward acting force) has to be present at P5 in order to balance the downward acting component along P2P5. Please help me! I'm having a migraine right now.