答案为100s.
108km/h=30m/s,列车从30m/s到到站停止用时50s,行驶距离750m,停车60s,从停止加速到30m/s用时30s,行驶距离450m,整个过程总时间为140s,总位移1200m.列车如果以30m/s通过这段位移只需用时40s,故延误的时间为140s-40s=100s.中间的计算过程省略.
还有种更简单的思路,列车从30m/s到到站停止用时50s,故延误的时间为25s,停车60s,从停止加速到30m/s用时30s,延误的时间为15s,故延误的时间为25s+60s+15s=100s.这个不好理解,画画V-T图简单明了.