Answer
4.5 m/s²
Explanation
Acceleration is defined as the rate of change of velocity with time.
The formula for finding acceleration is =change in velocity/change in time
change in velocity=15m/s - 6m/s=9m/s
change in time =2s-0s=2s
Acceleration is given by⇒9m/s ÷ 2s =4.5m/s²