Question

Your foot is trapped under a railway sleeper. You feel the rail vibrate and then 20s later hear a faint whistle. Estimate how much time you have to free yourself. You may assume the railway way is a straight line and: Velocity of sound in air = 0.33 km/s , The velocity of vibration along the track = 5 km/s,

Train speed: 60 km/hr, 100 km/hr and 150 km/hr

Answer 1

Step-by-step explanation:

Speed of sound in air = 0.33 km/s

Speed of vibration along the track = 5 km/s

Time = Distance / Speed

`(s)/(0.33)-(s)/(5)=20\\\Rightarrow (467)/(165)s=20\\\Rightarrow s=20* (165)/(467)\\\Rightarrow s=7.06638\ km`

When train speed: 60 km/hr

`Time=(7.06638)/((60)/(3600))=423.9828\ s`

Time you will have is 423.9828 s

When train speed: 100 km/hr

`Time=(7.06638)/((100)/(3600))=254.38968\ s`

Time you will have is 254.38968 s

When train speed: 150 km/hr

`Time=(7.06638)/((150)/(3600))=169.59312\ s`

Time you will have is 169.59312 s