Manipal MET2017PhysicsWaves and Sound
The apparent frequency of the whistle of an engine changes in the ratio 9: 8 as the engine passes a stationary observer. If the velocity of the sound is 340 ~ms ⁻¹ , then the velocity of the engine is
Options
- A40 ~ms ⁻¹
- B20 ~ms ⁻¹
- C340 ~ms ⁻¹
- D180 ~ms ⁻¹
Correct answer
A. 40 ~ms ⁻¹
Step-by-step solution
From Doppler's effect, perceived frequency aligned f^ & =f ( v-v_o v-v_s ) 9 8 & = 340 340-v_s aligned 9 (340-v_s )=8 340 v_s=37.7 ~ms ⁻¹ 40 ~ms ⁻¹