1).
Time = (distance) / (speed)
Time = (1000 meters) / (331 m/s)
Time = 3.02 seconds
2).
Acceleration = (change in speed) / (time for the change)
Change in speed = (second speed) - (first speed)
Change in speed = (50 m/s) - (20 m/s) = 30 m/s
Acceleration = (30 m/s) / (5 seconds)
Acceleration = 6 m/s²