You are the design engineer in charge of testing the crashworthiness of new automobile models. Cars are tested by smashing them into fixed, massive barriers at 50 km/h (30 mph). A new model of mass 1500 kg takes 0.15 s from the time of impact until it is brought to rest. Take the initial velocity of the car to be positive. (A) Calculate the average force exerted on the car by the barrier.