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A speeding motorcyclist sees traffic jam...

A speeding motorcyclist sees traffic jam ahead of him. He slows down to 36 km `cdot H^(-1) `. He finds that traffic has eased and a car moving ahead of him at `18 km cdot h^(-1) ` is honking at a frequency of 1392 Hz. If the speed of sound is 343 `m cdot s^(-1)`, the frequency of the honk as heard by him will be

A

1332 Hz

B

1372 Hz

C

1412 Hz

D

1454 Hz

Text Solution

Verified by Experts

The correct Answer is:
C
Speed of motorcyclist, `u_(o)=36" km" cdot h^(-1)=10m cdot s^(-1)`
Speed of car, `u_(s)=18" km" cdot h^(-1)=5m cdot s^(-1)`
Now, fundamental frequency of honk, v = 1392 Hz
`therefore lambda. = (V+u_(s))/n=(343+5)/1392=0.25 m `
Hence, frequency of honk as heard by the cyclist
`(V+V_(0))/(lambda.)=(343+10)/0.25=1412` Hz
The option (c) is correct.
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Knowledge Check

  • A speeding motorcyclist sees traffic jam ahead of him. He slows down to 36 km/hour. He finds that traffic has eased and a car moving ahead of him at 18 km/hour is horning at a frequency of 1392 Hz. If the speed of sound is 343 m/s.The frequency of the horn as heard by him will be

    A
    1332 Hz
    B
    1375 Hz
    C
    1412 Hz
    D
    1454 Hz

  • A siren emitting a sound of frequency 800 Hz moves away from an observer towards a cliff at a speed of 15 m cdot s^(-1) . Then the frequency of sound that the observer hears in the echo reflected from the cliff is (take velocity of sound in air = 330 m cdot s^(-1))

    A
    800 Hz
    B
    838 Hz
    C
    885 Hz
    D
    765 Hz

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