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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

340 m/s for passengers in A and 310 m/s for passengers in B

B

360 m/s for passengers in A and 310 m/s for passengers in B

C

310 m/s for for passengers in A and 360 m/s for passengers in B

D

340 m/s for passengers in both the trains

Text Solution

Verified by Experts

The correct Answer is:
B
`V_(SA)= 340 + 20 = 360 m//s`
`V_(SB) = 340 - 30 = 310 m//s`
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