A sports car travelling at uniform speed of 30 m s-¹ passes a police van which is cruising at 15 m s-¹. The van, accelerating at the rate of 1.2 m s-2, immediately begins to chase the car. (i) Write down expressions for the distance, s, travelled by each vehicle in t second, and hence (ii) calculate the time required for the van to overtake the car.