Algodoo

--Static equilibrium simulator--
Use the sliders to control the force of the red and blue cubes.
Drag the cubes to adjust their directions.

You can demonstrate how the ring remains in static equilibrium under the action of forces. The net force in both the X and Y directions is zero. For a more advanced explanation, you can use a paint tool to show Lami's Theorem.

--Update Log --
v1.1 Add angle markings every 15 degrees