The initial velocity is 0 (from rest) and the final velocity is 36 km/h
Average acceleration = 36 km/h - 0 36 km/h
---------------- = ---------------
20 seconds 20 seconds
We now convert 36 km/h to m/s as follows
36 km/h = 36 * 1000 m / 3600 s = 10 m/s
Hence
Average acceleration = 10 m/s
----------------- = 0.5 m/s squared
20 seconds
