Home
Class 11
PHYSICS
One train is approaching an observer at ...

One train is approaching an observer at rest and another train is receding from him with the same velocity `4 m//s` . Both trains blow whistles of same frequency of `243 H_(Z)` . The beat frequency in `H_(Z)` as heard by observer is (speed of sound in air = `320 m//s`)

A

10

B

6

C

4

D

1

Text Solution

Verified by Experts

The correct Answer is:
B
When the train is approaching
`n_1=(v)/(v-v_s)xxn=(320)/(320-4)xx243=(80)/(79)xx243`
When the train is receding,
`n_2=(v)/(v+v_s)xxn=(320)/(324)xx243=(80)/(81)xx243`
Beat frequency is
`n=n_1-n_2=80xx243((1)/(79)-(1)/(81))=6Hz`
Promotional Banner

Topper's Solved these Questions

  • SOUND WAVES AND DOPPLER EFFECT

    CENGAGE PHYSICS ENGLISH|Exercise Multiple Correct|44 Videos

  • SOUND WAVES AND DOPPLER EFFECT

    CENGAGE PHYSICS ENGLISH|Exercise Assertion-Reasoning|24 Videos

  • SOUND WAVES AND DOPPLER EFFECT

    CENGAGE PHYSICS ENGLISH|Exercise Subjective|56 Videos

  • RIGID BODY DYNAMICS 2

    CENGAGE PHYSICS ENGLISH|Exercise Interger|2 Videos

  • SUPERPOSITION AND STANDING WAVES

    CENGAGE PHYSICS ENGLISH|Exercise Comprehension Type|5 Videos

Similar Questions

Explore conceptually related problems

One train is approaching an observer at rest and another train is receding him with same velocity 4 ms^(-1) . Both the trains blow whistles of same frequency of 243 Hz. The beat frequency in Hz as heard by the observer is (speed of sound in air= 320ms^(-1) )

A person is observing two trains, one is approaching him with a velocity of of 4 m/s while the other is receding from him with the same velocity. IF both the trains blow their respective whistles of frequency 240 hertz, the beat frequency heard by the observer will be (speed of sound in air = 320 m/s)

A train is moving with speed 72 km/h towards a hill blows a whistle of frequency 1240Hz. the frequency of echo heard by driver is(speed of sound=330m/s)

On a platform a man is watching two trains one leaving the station the other approaching the station, both with the same velocity 2 m/s and blowing their horn with a frequency 480 Hz. The number of beats heard by the man will be (Velocity of sound in air is 320 m/s)

A person is listening to two trains one approaching him while the other moving away from him. The speed of both the trains is 5 m/s. If both trains give off whistle of their nature frequency of 280 Hz then the observer will hear ... no of beats/s. (Velocity of sound = 350 m/s)

A car travelling towards a hill at 10 m//s sound its horn which a frequency 500 H_(Z) . This is heard in a second car travelling behind the first car in the same direction with speed 20 m//s . The sound can also be heard in the second car by reflections of sound the hill. The beat frequency heard by the driver of the sound car will be (speed of sound in air = 340 m//s)

An observer a sitting on a cart executing SHM between A and B listens to a whistle which rotates in a circle with constant speed 5 m/s as shown.The maximum speed of the car is same as that of whistle . If frequency of the whistle is 640 Hz,then maximum possible frequency observed by observer is [Speed of sound in air= 320 m/s]

A man is watching two trains, one leaving and the other coming in, with equal speed of 4 m/s. If they sound their whistles, each of natural frequency of 240 Hz, the number of beats beard by the man (velocity of sound in air = 300 m/s ) will be equal to

Two tuning forks A and B lying on opposite sides of observer 'O' and of natural frequency 80 Hz move with velocity 10 m//s relative to stationary observer O . Fork A moves away from the observer while the fork B moves towards him. A wind with a speed 10 m//s is blowing in the direction of motion of fork A . Find the beat frequency measured by the observer in Hz. [Take speed of sound in air as 340 m//s ].

A whistle giving out 450 H_(Z) approaches a stationary observer at a speed of 33 m//s . The frequency heard the observer (in H_(Z) ) is (speed of sound = 330 m//s )

CENGAGE PHYSICS ENGLISH-SOUND WAVES AND DOPPLER EFFECT-Single Correct
  1. Two sources A and B are sounding notes of frequency 680 Hz. A listener...

    Text Solution

    |

  2. A train has just completed a U-curve in a trach which is a semi circle...

    Text Solution

    |

  3. One train is approaching an observer at rest and another train is rece...

    Text Solution

    |

  4. Two sound sources are moving in opposite directions with velocities v...

    Text Solution

    |

  5. the frequency changes by 10 % as the source approaches a stationary ob...

    Text Solution

    |

  6. speed of sound wave is v. if a reflector moves toward a stationary so...

    Text Solution

    |

  7. An observer moves towards a stationary source of sound with a speed 1/...

    Text Solution

    |

  8. A source of sound S is moving with a velocity of 50m//s towards a stat...

    Text Solution

    |

  9. A whistle emitting a sound of frequency 440 Hz is tied to a string of ...

    Text Solution

    |

  10. A band playing music at a frequency v is moving towards a wall at a sp...

    Text Solution

    |

  11. A man standing on a platform hears the sound of frequency 604 Hz comin...

    Text Solution

    |

  12. A vehicle , with a horn of frequency n is moving with a velocity of 30...

    Text Solution

    |

  13. An isotropic stationary source is emitting waves of frequency n and wi...

    Text Solution

    |

  14. A train is moving with a constant speed along a cirular track. The eng...

    Text Solution

    |

  15. An observer moves towards a stationary source of sound with a velocity...

    Text Solution

    |

  16. An increase in intensity level of 1 dB implies an increase in intensit...

    Text Solution

    |

  17. In expressing sound intensity we take 10^(-12)(W)/(m^2) as the referen...

    Text Solution

    |

  18. The intensity level of two sounds are 100 dB and 50 dB. What is the ra...

    Text Solution

    |

  19. An engine running at speed (v)/(10) sounds a whistle of frequency 600 ...

    Text Solution

    |

  20. A source of sound produces waves of wavelength 60 cm when it is statio...

    Text Solution

    |