(b) For no collision, the speed of car A should be reduced to vB before the cars meet, i.e. final relative velocity of car A with respect to car B is zero, i.e. vrelative =0 Here, initial relative velocity, ur=vA−vB Relative acceleration, ar=−a−0=−a Let relative displacement be sr. Thus, from third equation of motion, we get vrelative 2=ur2+2arsr=(vA−vB)2−2asr ⇒sr=