Two cars X and Y are approaching each other with velocities 36 km/h and 72 km/h respectively. The frequency of a whistle sound as emitted by a passenger in car X, heard by the passenger in car Y is 1320 Hz. If the velocity of sound in air is 340 m/s, the actual frequency of the whistle sound produced is .................. Hz.
Answer (integer)
1210
Solution
Image<br><br>V<sub>x</sub> = 36 km/hr = 10 m/s<br><br>V<sub>y</sub> = 72 km/hr = 20 m/s<br><br>by doppler's effect<br><br>$F' = {F_0}\left( {{{V \pm {V_0}} \over {V \pm {V_s}}}} \right)$<br><br>$$1320 = {F_0}\left( {{{340 + 20} \over {340 - 10}}} \right) \Rightarrow {F_0} = 1210$$ Hz
About this question
Subject: Physics · Chapter: Waves · Topic: Wave Motion and Types
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