有没有物理帝帮忙算一个得数!TheShinkansen,theJapanese"bullet"train,runsathighspeedfromTokyotoNagoya.RidingontheShinkansen,younoticethatthefrequencyofacrossingsignalchangesmarkedlyasyoupassthecrossing.Asy

Question

有没有物理帝帮忙算一个得数!
The Shinkansen, the Japanese "bullet" train, runs at high speed from Tokyo to Nagoya. Riding on the Shinkansen, you notice that the frequency of a crossing signal changes markedly as you pass the crossing. As you approach the crossing the frequency you hear is f; as you recede from the crossing the frequency you hear is 5f /9. What is the speed of the train?

Answer 1

新干线是日本的子弹头火车,在东京到名古屋一线高速行驶.乘坐在新干线列车上,当经过道口的时候,你听到道口的（声音）信号的频率发生了明显的变化.当你接近道口的时候,你听到的频率是f；当你远离道口的时候,你听到的频率是5f/9.试求列车的速度.
吐槽：新干线列车是封闭的,你不太容易听到外面的声音……
声速v0=340m/s,设列车速度为v.
则(v0+v)/(v0-v)=f/(5f/9),计算出v=2v0/7,即列车的速度是声速的2/7,即97.1m/s,或349.7km/h.