....or the continuous increasing of an unbalance,can be acquired,if we connect a neutral stability ,with a negative stability.
Negative stability tends to increase an incipient disturbance (see gravity).
Neutral stability tends to maintain constant an incipient disturbance (see inertia).
If we apply the negative stability to a mass "m" ,and we couple,pair this one ,with a neutral stability of a mass "M" ,we have as a result a negative dynamic stability.
The interesting point is,when...M>>>m...
All the best! / Alex