When a node is fixed to a roller, it is only permitted to move along a straight line-the direction of the roller. Consider the three bar structure in Example 6.5. Suppose node 1 is fixed, but node 4 is attached to a roller that only permits it to move in the horizontal direction.
(a) Construct the reduced incidence matrix and the equilibrium equations in this situation. You should have a system of 5 equations in 5 unknowns-the horizontal and vertical displacements of nodes 2 and 3 and the horizontal displacement of node 4.
(b) Is your structure stable? If not, how many rigid motions and how many mechanisms does it permit?