A train is moving on a straight track with speed 20 ms^–1. It is blowing its whistle at the frequency of 1000 Hz. The percentage change in the frequency heard by a person standing near the track as t…

Question

A train is moving on a straight track with speed 20 ms^–1. It is blowing its whistle at the frequency of 1000 Hz. The percentage change in the frequency heard by a person standing near the track as the train passes him is (speed of sound = 320 ms^–1) close to

Accepted Answer

Correct answer: B. (b) f_ before crossing=f_0 ( cc-v_s )=1000 ( 320320-20 ) f_ after crossing=f_0 ( cc+v_s )=1000 ( 320320+20 ) f=f_0 ( 2cv_sc^2-v_s^2 ) ff 100 \%= 2 320 20300 340 100=12.54 \% ≈12 \%

$A train is moving on a straight track with speed 20 m s^{-1} . It is blowing its whistle at the frequency of 1000 Hz. The percentage change in the frequency heard by a person standing near the track as the train passes him is (speed of sound = 320 m s^{-1}) close to$

Solution

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