To see how an explicit mass-spring system causes instability, let us consider a single 1D spring. One end of the spring is attached to the origin, and the other end is attached to a particle with mass 1. The spring length is initially 1, so the particle is located at x = 1. Suppose the time step Δt is 1 and the spring stiffness is 10, we can formulate the whole system as: 

 If we move the particle to x ⁰ = 2 and then release it with no initial velocity (v ⁰ = 0), where is the particle located at time t = 1? Where is the particle located at time t = 2? Where is the particle located at time t = 3?

vt+1 = yt 10(|| 1), at+1 = at+ot+1. xt- (1)