Q:

How do masses on a spring accelerate when the connection between them is cut?

I'm learning about springs in Physics and have come across something I do not fully understand.
As in the picture, there are three masses (A, B and C), with mass ma, mb and mc, respectively. In the configuration above, masses A and B are connected by a light inelastic string. The masses of the string and the two springs are negligible and the whole system is stationary (in equilibrium).
What I want to work out is the acceleration of the three masses when the string between A and B is suddenly cut.
I currently understand from slinkies that C would stay stationary while S2 contracts. So B is accelerating downwards. Therefore, C would have no acceleration.
Also, S1 is carrying all three masses but after the string is cut, it only carries ma, so it would contract upwards with a force equivalent to g(mb+mc), because they are the forces taken away from the spring. But when I calculate the acceleration of A using F=ma, I end up with a=g and I am not sure if that is correct, because I also get a=g for the acceleration of B.
I am trying to express each acceleration in terms of ma, mb, mc and g.
I am not looking for answers, as I know this is not a homework site. All I ask is for pointers in the right direction and perhaps correct me if my understanding of the spring system is flawed.
Thank you.

A:

When the connection between A & B is cut, mass of B & C is removed from the spring. When the masses B & C were attached, they exerted some force on the spring causing extension. They are removed so the spring will relax and extension in it will be reduced. Mass A will be accelerated upwards and will start performing simple harmonic motion. As for the masses B & C, gravitational force will pull them down. They will be in free- fall and therefore mass C will not pull the spring downward as it was doing in initial conditions. So, the spring will relax and come back to it's natural length. Coming back to it's natural length, it will exert an upward force on C and downward force on B.  

