The Defold examples show individual concepts and features of Defold.
This example shows a simple setup with a static pivot and two dynamic weights - physics objects joined together with a joint of type "fixed" and "spring". The fixed joint can simulate a rope and spring joint a spring. The example shows how to create the joints and change the gravity to affect the pendulums.
This example shows a simple setup with a dynamic body physics object and two dynamic wheel physics object joined together with a joint of type "hinge". The hinge joint can simulate an axle or a pin on which other object is rotating in respect to the base. The example shows how to create, destroy and change properties of the joints.