question_answer

A train approaching a railway crossing at a speed of 120 km/h sounds a short whistle at frequency 640 Hz when it is 300 m away from the crossing. The speed of sound in air is 340 m/s. What will be the frequency (in Hz) heard by a person standing on a road perpendicular to the track through the crossing at a distance of 400 m from the crossing?

Answer:

680