A $0.20\,\text{kg}$ mass hangs from the lower end of a light spring. A $0.10\,\text{kg}$ mass is then attached to this first mass by a thread. The system is left to reach static equilibrium, and then the thread is severed. At the instant just after the thread is severed, what upward acceleration does the $0.20\,\text{kg}$ mass have?
- A$4.9\,\text{m s}^{-2}$
- B$6.5\,\text{m s}^{-2}$
- C$9.8\,\text{m s}^{-2}$
- D$15\,\text{m s}^{-2}$