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A person riding a car moving at `72 km h^-1` sounds a whistle emitting a wave of frequency 1250 Hz. What frequency will be heard by another person standing on the road (a) in front of the car (b) behind the car ? Speed of sound in air `= 340 m s^-1` .

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The correct Answer is:
A, B, C
a. Given `v_s=72km/hour`
`=20 m/s, F=1250Hz`
Apparent frequency
`=(340+0+0)/(340+0-20)xx1250`
`=1328Hz`
For second case Apparent frequency
`=((340+0+0)/(340+0-(-20))xx1250`
`=340/360xx1250=1181Hz
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HC VERMA-SOUND WAVES-All Questions
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  2. The horn of a car emits sound with a dominant frequency of 2400 Hz. Wh...

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  3. A person riding a car moving at 72 km h^-1 sounds a whistle emitting a...

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  4. A train approaching a platform at a speed of 54 km h^-1 sounds a whist...

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  5. A bat emitting an ultrasonic wave of frequecy 4.5 xx 10^4 Hz flies at...

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  6. A bullet passes past a person at a speed of 220 m s^-1. Find the fract...

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  7. Two electric trains run at the same speed of 72 km h^-1 along the same...

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  8. A violin player riding on a slow train plays a 440 Hz note. Another vi...

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  10. A small source of sound vibrating at frequency 500 Hz is rotated in a ...

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  11. Two trains are travelling towards each other both at a speed of 90 km ...

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  12. A traffic policeman sounds a whistle to stop a car-driver approaching ...

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  13. A car moving at 108 km h^-1 finds another car in front of it going in ...

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  14. Two submarines are approaching each other in a calm sea. The first sub...

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  15. Sound travels with a speed of 330 ms^(-1). What is the wavelength of s...

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  16. A boy riding on his bike is going towards east at a speed of 4sqrt2ms^...

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  17. A sound source, fixed at the origin, is continuously emitting sound at...

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  18. A car moves with a speed of 54 kmh^-1 towards a cliff. The horn of the...

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  19. An operator sitting in his base camp sends a sound signal of frequency...

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  20. Figure shows a source of sound moving along the X-axis at a speed of 2...

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