Question 709611
At the start your speed is 0 km/hr.  After moving and accelerating for 5 seconds your speed is 60 km/hr.  Acceleration is [change in rate] divided by [change in time].  


Here the units are changed first to seconds instead of hours, but your purposes may justify not other time units.


(60 km/hour) * (1 hour/60 min) * (1 min/60 sec) = 1/60 km/sec


Look at the data.
final rate = 1/60 km/sec
initial rate = 0  km/sec
final time = 5 sec
initial time = at 0 sec


Acceleration = {{{(1/60-0)/(5-0)=(1/60)/5}}}
={{{5/60}}}={{{highlight(1/12)}}}, in units of {{{highlight(km/s^2)}}}