4.In a vehicle impact, a car ran into the back of a lorry. The car driver sustained serious injuries, which would have been much less had the car been fitted with a driver's air bag. (a)Explain why the effect of the impact on the driver would have been much less if an air bag had been fitted and had inflated in the crash. (b)Calculate the deceleration of the car if it was travelling at a speed of 18 m s when the impact occurred and was brought to rest in a distance of 2.5 m. (4) (2) (Total 6 marks)