Question

Two trains are travelling towards each other both at a speed of 90 km h−1. If one of the trains sounds a whistle at 500 Hz, what will be the apparent frequency heard in the other train? Speed of sound in air = 350 m s−1.

Answer 1

The Apparent Frequency is 376.9 Hz

Explanation:

The apparent frequency heard by the other train is given by,

• f = $(\frac {v + v_0}{v - v_s})f_0$

Here,

v = 350 $ms^-1$

$V_0$ = 90 kmph = 25 $ms^-^1$  

$f_0$ = 500 Hz

So,  

f = $(\frac {350 + 25}{350 - 25}) \times 500$ Hz

f = 376.9 Hz