1.车辆在水平地面上以恒定功率起动 车辆以恒定功率起动,随着速度的增加,由P0=Fv可知,车辆的牵引力减小,而速度增加也使得它所受的阻力变大,由a=F-f/m可知,车辆的加速度变小,速度的增加变慢,这样,循环往复……如图1所示.当车辆的加速度减至零时,其速度达到最大值vm,即vm=P0/F,且有F=f.此后,车辆匀速运动. 例1 质量为m=5.0×106kg的列车,由 1. The vehicle starts on a level ground with a constant power to start the vehicle at a constant power. As the speed increases, P0 = Fv shows that the traction force of the vehicle decreases, and the increase in speed also increases the resistance it receives. =Ff/m It can be seen that the acceleration of the vehicle becomes smaller and the increase of the speed becomes slower, so that the cycle is reciprocated as shown in Fig. 1. When the acceleration of the vehicle is reduced to zero, the speed reaches a maximum value vm, that is, vm=P0 /F, and there is F = f. Thereafter, the vehicle moves at a constant speed. Example 1 The train of mass m = 5.0 × 106kg consists of