Given, acceleration of cars A and B is a1 and a2, initial velocities of cars A and B are zero, final velocities of car A and B are v1 and v2, respectively. Distance between cars A and B,s=50m Net acceleration, a‌net ‌=4ms−2 By using second equation of motion, v2−u2=2as ∴‌‌(v1−v2)2−0=2(a1−a2)s ⇒‌‌(v1−v2)2=2×4×50=400 ⇒‌‌v1−v2=20ms−1