Here in all such collision type question we can use momentum conservation as we can see that there is no external force on this system

as we know that




now from above equation we have



so the speed of combined system is 2 m/s
Magnitude of acceleration = (change in speed) / (time for the change) .
Change in speed = (ending speed) - (starting speed)
= zero - (43 m/s)
= -43 m/s .
Magnitude of acceleration = (-43 m/sec) / (0.28 sec)
= (-43 / 0.28) (m/sec) / sec
= 153.57... m/s²
= 1.5... x 10² m/s² .
The correct answer would be D