一质量为500t的机车，以恒定功率375kW由静止出发，经过5min速度达到最大值54km/h，设机车所受阻力f恒定不变，取

g=10m/s²，试求：

（1）机车受到的阻力f的大小．

（2）机车在这5min内行驶的路程．

Software document is an important part of software and a basis of software development phase. It also influences software's( ).

A．reusability

B．maintenance

C．expansibility

D．portability