问题
问答题
⑴列车在行驶过程中所受的阻力大小．
⑵列车的额定功率．
⑶列车从开始运动到停下所经过的总路程
答案
（1）6×104 N（2）
（3）14 km
⑴依题意可求刹车时列车的加速度
················· 2分
由牛二律，得
················································· 2分
代入数据可求得
＝6×104 N················································ 2分
⑵列车的额定功率
··········· 4分
⑶对列车运动全过程由动能定理有
····················· 4分
代入数据可求得s1＝1.4×104 m＝14 km································· 2分