Two steel balls of 2 kg and 4 kg mass, respectively, are pressed on the two ends of a spring, all pre-placed on a smooth surface. When released, the smaller ball moves with an acceleration of 2 m/s2. The simultaneous acceleration of the bigger ball will be
1
0.5 m/s2
2
1 m/s2
3
2 m/s2
4
4 m/s2