题目

Whilethe National Congress of Communist Party, President Xi instructed the party never to forget we started and then we can accomplish our mission. A . delivering; when B . announcing; why C . claiming; when D . addressing; why 答案：D质量为500吨的机车以恒定的功率由静止出发，经5min行驶2.25km，速度达到最大值54km/h，设阻力恒定．问：（1）机车的功率P多大？（2）机车的速度为36km/h时机车的加速度a多大？