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Two trains A and B moving with speeds 20...

Two trains `A and B` moving with speeds `20m//s` and `30m//s` respectively in the same direction on the same straight track, with `B` ahead of `A`. The engines are at the front ends. The engine of train `A` blows a long whistle.
Assume that the sound of the whistle is composed of components varying in frequency from `f_(1) = 800 Hz` to `f_(2) = 1120 Hz`, as shown in the figure. The spread in the frequency (highest frequency - lowest frequency) is thus `320 Hz`. The speed of sound in still air is `340 m//s`.
(4) The speed of sound of the whistle is

A

B

C

D

Text Solution

Verified by Experts

The correct Answer is:
A
Since whistle is sounded by the train A and passengerss in the same train are also moving in the same direction as that of the source with the same speed. Hence, there will be no change in the observed frequency. Hence option (a) is correct.
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