Here's another example exploring what can be done:
https://www.dropbox.com/s/4o28kqq4b30pb ... .capx?dl=1
I commented it a lot and in many ways it's cleaner than what I've done before. I'm figuring it out as I go and unfortunately it would be too lengthy of a tutorial for me to write. Math used is some simple physics such as:
distance = speed* time
speed = acceleration * time
acceleration = force*mass
spring_force = -spring_constant * displacement
damping_force = -damping_constant * relative_velocity
Also vectors are used. addition, subtraction and dot product.
The dot product is used to get the speed in a certain direction.
Some simple trig is used too.
x = radius*cos(ang)
y = radius*sin(angle)
The collision detection uses the dot product to get the distance from a line. Otherwise everything is a mix of that.
There are two unsolved things in this:
1. The spring mesh can be made to fold in on itself.
2. The balls can teleport through walls if either are going fast enough.