[填空题]
You are the design enga(c-ng ;ejwv 8ineer in charge of the crashworthiness of new autom oo r4m+fz-o-cobile models. Cars are tested by smashing them into fixed, massive barriers at 50km/h (30 mph). A new model of mass 1500 kg takes 0.15 s from the time of impact until it is broug4f+-o-mz o croht to rest. (a) Calculate the average force exerted on the car by the barrier. $\approx$$a\times10^5$N a =
(b) Calculate the average deceleration of the car. m/$s^2$
