Bridges
Introduction:
Bridges are:

Mostly a physics system problem that involving sticks that are connected to each other
by springs on their end points, where the sticks on the end are connected to anchor points.
Understanding the problem(s):
 Q: What needs to be calculated each frame, and how?
A:
 Stick center of mass position.
 Stick inertia tensor.
 Linear force on the two endpoints of the stick.
 Torque at the end points of the stick.
Solving the problem(s):