Let the acceleration of the car is =a and the distance between A and B is =d
v2−u2=2ad
Given,
v=30m/s and u=20m/s
2ad=302−202
ad=(900−400)2=250
when the car is at the mid point of AB then let the speed of the car is
v1
v21−202=2a(d2)
v21=ad+400=250+400=650
therefore
v1 is =25.5m/s