v1 = 28 m/s
v0 = 0 m/s *
v1 = v0+at v1-v0 = at (v1-v0)/a = t
For the values given and assumed (*) we get t = (28-0)/5.3 = 5.3 s
What we have calculated is the difference in speed we want to achieve divided by how quickly we can increase the speed.