First, create an illustration of the motion of the two cars as shown in the attached picture. The essential equations used is
For constant acceleration:
a = v,final - v,initial /t
The solutions is as follows:
a = v,final - v,initial /t
3.8 = (v - 0)/2.8 s
v = 10.64 m/s After 2.8 seconds, the speed of the blue car is 10.64 m/s.
Given :
Current, I = 3.75 A .
Magnetic Field, 
To Find :
The distance from the wire.
Solution :
We know,

Hence, this is the required solution.
Huh? The answer is A Shadow
We use only one variable at a time to find the accurate result. We want to see how the result of experiment changes everytime with a single variable.