Free-body diagrams
Annotate → Free-Body Diagram, then click a body (a support too). The body's outline is drawn alone beside it, with every force that acts on it as a labelled arrow at its point of application, taken from the engine's last step. Drag the diagram anywhere; Properties → On the body draws the arrows on the body instead.
| Force | Label |
|---|---|
| weight | mg (m_1g for a body named m₁) |
| contact: normal, friction, rolling resistance — one per touching body | N, F_f, M_r (numbered with several partners) |
| cable | T |
| pin, weld, slider | R, or R_x and R_y (Reactions as x and y components); a weld's or slider's moment M |
| pin torques | τ_s spring, τ_f friction, τ_stop angle stop, τ_m motor |
| rod, spring, gear tooth, belt | F_r, F_s, F_t, τ_b |
| thruster, applied load, air | F_T, F(t) / τ(t), F_D |
| a support's or a fixed axle's reaction | R, R_axle |
Properties → Free-body diagram has the options — Values on the arrows (N = 26.67 N), Arrow lengths to scale, reactions as components — and read-outs: every force with its value, ΣF and ΣM about the centre. For a body at rest both sums are zero (for a moving one ΣF = m·a), which makes the diagram a check of the statics.
The forces are those of the last simulated step: run or step a new scene once to see contacts and reactions. Diagrams are saved with the scene and drawn in every export (TikZ labels as math: $N=26.67\,\mathrm{N}$).
Member forces
Analyze → Member Forces colours every rigid rod by its axial force — tension red, compression blue — with its value beside it (29.4 N (C)), as in the method of joints. Build the truss from rods joined at pins (the Marketplace's examples from Ordinate 2D have one under Statics and structures, checked against the method of joints). Bars from the Bar tool are solid bodies, not rods: for a bar's force use a free-body diagram.
How accurate
The forces come from the solver, not from a separate statics calculation. The Validation page compares them with hand calculations: a block on an incline, the Atwood machine's tension and a beam's pin reactions agree to better than 0.01 %.