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在教授《功、功率》这一节中,汽车的两种启动方式有两种:以恒定功率启动、以恒定加速度启动.这两只启动的方式不同,如果最后都达到了匀速运动,启动过程中消耗的能可能不同,那么哪种启动方式汽车做功更多呢?下面详细分析.如果汽车以恒定功率P启动,其v-t图像如图1所示,由P=Fv可知汽车刚启动时,速度很小所以牵引力很大.但随着速度慢慢增加牵引力就减小了,所以汽车做的是加速度减小的加速运动.直到t B时刻汽车的牵引力减小到等于阻力时即图像中的B点,此后汽车做匀速直线运动.
In the section titled “Power, Power”, there are two ways to start a car: Start at a constant power and start at a constant acceleration The two start up differently, and if they reach a constant speed at the end, the start-up process If the car starts with a constant power P, its vt image shown in Figure 1, from P = Fv shows that the car just started, the speed Very small so the traction is great, but as the speed slowly increases the traction is reduced, so the car is accelerating acceleration to reduce the acceleration until t B when the car’s traction is reduced to equal resistance when the image B Point, since the car to do uniform linear motion.