Tensegrity
This activity belongs to the GeoGebra book GeoGebra Principia.
Elastic geometry allows us to find equilibrium situations between different forces. An interesting application is tensegrity structures, composed of bars and tensioned cables that hold them together.
When we connect different vertices, we obtain the graph of this set of vertices [25]. But if the connections are made up of bars and springs, we can achieve that in certain positions, the tension of the springs balances out in a stable structure, called a tensegrity 
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Here is an example in the plane. Because the rhombus is a parallelogram, the forces at each vertex cancel out, so the structure remains in stable equilibrium in any position, as long as the horizontal and vertical tensions are equal.
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Here is an example in the plane. Because the rhombus is a parallelogram, the forces at each vertex cancel out, so the structure remains in stable equilibrium in any position, as long as the horizontal and vertical tensions are equal.Author of the construction of GeoGebra: Rafael Losada.