I had once programmed a 2D rigid body physics simulator that I called “ISAAC”. Here are some cool animations made in it.
Notice how the collisions change when I change the coefficient of restitution.
Coefficient of restitution = 0
Coefficient of restitution = 0.5
Coefficient of restitution = 1
Energy completely conserved!
Since the program works on a computer, reality doesn’t matter.
Coefficient of restitution = 1.5
Energy created in every collision!
Coefficient of restitution = -1
I DON’T EVEN KNOW!
Thanks for looking.