Physics

Problem

Two trains, A and B, move on parallel tracks towards a stationary observer O. Train A’s whistle has a frequency of

500\,\text{Hz}

and approaches O with a speed of

15\,\text{m\,s}^{-1}

. Train B’s whistle has a frequency of

480\,\text{Hz}

. The observer hears

5

beats per second and notes that the pitch coming from train B is lower than that from train A. Calculate the speed of train B. (Speed of sound in air

=340\,\text{m\,s}^{-1}

.) a)

26\,\text{m\,s}^{-1}

25\,\text{m\,s}^{-1}

31\,\text{m\,s}^{-1}

24\,\text{m\,s}^{-1}