例1(2011,浙江卷)节能混合动力车是一种可以利用汽油及所储存电能作为动力来源的汽车。有一质量m=1000 kg的混合动力轿车,在平直公路上以v_1=90 km/h匀速行驶,发动机的输出功率为P=50 kW。当驾驶员看到前方有80 km/h的限速标志时,保持发动机功率不变,立即启动利用电磁阻尼带动的发电机工作给电池充电,使轿车做减速运动,运动L=72 m后,速度变为v_2=72 km/h。此过程中发 Example 1 (2011, Zhejiang Volume) An energy-saving hybrid car is a car that uses gasoline and stored energy as a source of power. A hybrid car with a mass of m = 1000 kg drives at a constant speed of v_1 = 90 km / h on a straight road with an output power of P = 50 kW. When the driver saw the 80 km / h speed limit in front of the sign, keep the engine power unchanged, immediately start using the electromagnetic damping driven generator to charge the battery, so that the car to do slow motion, movement L = 72 m, The speed becomes v_2 = 72 km / h. In this process hair