Let me consider a spring fixed to one end and a mass(call m1) attached to other end.

when i apply a force f to the mass(m1) it shouldl accelerate to a=f/m1 if newtons law is to be obeyed.

But since the spring has a restoring force the mass doesn't accelerate. But at what time the restoring force comes in to picture. Will the spring take some time before it applies a restoring force=applied force. If it takes some time to apply restoring force in that duration the force f must have given the mass m a much higher acceleration and .............. the mass will accelerate. I need some discussion on this ........