Acceleration = (change in velocity) / (time for the change)
that's = (change in speed and its direction) / (time for the change)
Change in velocity = (ending velocity) - (starting velocity)
Change in velocity = (20 m/s west) - (15 m/s west)
Change in velocity = 5 m/s west
Acceleration = (5 m/s west) / (5 seconds)
Acceleration = 1 m/s west
