This Demonstration determines whether a truss can be solved or if it is statically indeterminate by calculating the number of equations and the number of unknowns. Use buttons to make joints either rollers (one reaction force) or pinned (two reaction forces). Eliminate joint by unchecking "support at joint ". The number of members, joints and reaction forces is shown above the truss. Check "joint labels" to show labels for each joint. The point load forces are green (known forces) and the reaction forces (unknown forces) are blue.