What This Calculator Does
A truss joint looks simple, but each member can hide a different axial force. This calculator applies the method of joints to one selected node. It balances horizontal and vertical forces at that point. The tool is useful after support reactions are known, or after nearby members have already been solved.
Why Joint Equilibrium Matters
A pin joint cannot carry a bending moment in the ideal truss model. Each member force acts along its own centerline. External loads, reactions, and known member forces must therefore sum to zero in two directions. When the joint has two unknown member forces, the equations form a small linear system. Solving that system gives signed axial values. Positive values mean tension. Negative values mean compression.
Practical Input Strategy
Start with a joint that has only two unknown members. Enter each unknown member angle from the positive horizontal axis. Use positive external force for rightward or upward action. Use negative values for leftward or downward action. Add any known member forces that already act on the same joint. Keep one unit system through the whole calculation. Mixing pounds and newtons will give poor results.
Reading the Result
The result table lists each unknown force, its direction, and its state. A compression result means the member pushes toward the joint. A tension result means it pulls away from the joint. The residual row checks the final balance. Very small residuals are normal because of rounding. Large residuals usually mean a wrong angle, sign, or known force.
Design Use
The method of joints is a first analysis step. It does not replace code checks. Real trusses also need buckling review, connection design, load combinations, and deflection checks. Still, this calculation is valuable. It shows the force path through a structure. It also helps students understand why every joint must balance. Use the export buttons to save the solved case for homework, review notes, or field records. Good checks also improve teamwork. A clear table lets another reviewer repeat the same assumptions. Angles, signs, and units are visible. This reduces confusion during classroom work, shop planning, or early design comparison. Save the inputs with the answer whenever decisions depend on the force values later.