Question

Two trains are approaching each other on parallel tracks
with same velocity. The whistle sound produced by one
train is heard by a passenger in another train. If actual
frequency of whistle is 620Hz and apparent increase in
its frequency is 100Hz, the velocity of one of the two
trains is (Velocity of sound in air = 335 ms)
1) 90 kmph 2) 72 kmph 3) 54kmph 4) 36 kmph​

Answer 1

Answer:

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Answer 2

Answer:

1) 90 kmph

Explanation:

Given: δ = 620 Hz

δ' = (620 + 100) Hz = 720 Hz

$v_{0}$ = $-v_{s}$ = -v m/s

v = 335 m/s

By doppler effect formula:

δ' = δ ($\frac{v - v_{0} }{v - v_{3} }$)

720 = 620 ($\frac{335 + v}{335 - v}$)

335 (720) - 720v = 620 (335) + 620v

v = 25 m/s

= 25 × $\frac{3600}{1000}$ km/h

= 90 km/h

-$Shahrin$ $Khan$