The force acting on the smaller cart is from the spring, and equals 30N. The acceleration of that cart would be 15 m/s^2. The acceleration of the system after the spring stretching has stabilized would be, I think, the same as just the small block because the system would be moving as a whole.
Knowing that F=k*deltaX I figure that the spring is stretched with a force of 30N. But that answer doesn't seem to be right. I know it must have something to do with the other mass at the end of the spring but I don't know how that would relate.
Homework Statement
A 2.0-kg cart and an 8.0-kg cart are connected by a relaxed, horizontal spring of spring constant300 N/m. You pull the 8.0-kg cart with some constant horizontal force. The separation between the carts increases for a short time interval, then remains constant as you continue...