Velocity of car A, v_{A} = 36 km/h = 10 m/s

Velocity of car B, v_{B} = 54 km/h = 15 m/s

Velocity of car C, v_{C} = 54 km/h = 15 m/s

Relative velocity of car B with respect to car A,

vBA = vB – vA = 15 – 10 = 5 m/s

Relative velocity of car C with respect to car A,

vCA = vC – (– vA) = 15 + 10 = 25 m/s

At a certain instance, both cars B and C are at the same distance from car A i.e.,

s = 1 km = 1000 m

Time taken (t) by car C to cover 1000 m = 1000/25 = 40s

Hence, to avoid an accident, car B must cover the same distance in a maximum of 40 s. From second equation of motion, minimum acceleration (a) produced by car B can be obtained as: