Home
Class 11
PHYSICS
A train standing a the outer signal of a...

A train standing a the outer signal of a railway station blows a whistle of frequency 400Hz in still air .
What is the frequency of the whistle for a platform observer when the train
(i) approaches the platform with a speed of `10ms^(-1)` ?
(ii) recedes from the platform with a speed of `10 ms^(-1)` ?

Text Solution

Verified by Experts

(i) given `f=400 Hz, v_s=10 ms^(-1).`
(a) For a source approaching the stationary observer, on the platform, apparent frequency
`f'=f((v)/(v-v_s)),v-v_s=340-10=330 ms^(-1)`.
`& v+v_3=340+10=350 ms^(-1). = (400xx340)/(330)`
`f=412.1 Hz` ie apparent frequency `=412 Hz`
(b) For a source receding away from the stationary observer apparent frequency
`f'=f((v)/(f+v_s))=(400xx340)/(350)=388.6 Hz`
i.e. `f'=387 Hz.`
Promotional Banner

Topper's Solved these Questions

  • PU BOARD MODEL QUESTION PAPER (WITH ANSWERS)

    SUBHASH PUBLICATION|Exercise EXERCISE (PART - C)|8 Videos

  • PHYSICAL WORLD

    SUBHASH PUBLICATION|Exercise TWO MARKS QUESTIONS WITH ANSWERS|30 Videos

  • SUPER MODEL QUESTION PAPER (WITH ANSWERS)

    SUBHASH PUBLICATION|Exercise PART - D|11 Videos

Similar Questions

Explore conceptually related problems

A train standing a the outer signal of a railway station blows a whistle of frequency 400Hz in still air . when the train (i) approaches the platform with a speed of 10ms^(-1) ? (ii) recedes from the platform with a speed of 10 ms^(-1) ? What is the speed of sound in each case ? The speed of sound in still air can be taken as 340ms^(-1)

A train at rest blows a whistle of frequency 600 Hz in still air. What is the frequency of whistle for a platform observer when the train.(a) approaches the platform with a speed of 15 ms^(-1) (b) recedes from the platform with a speed of 15 ms-l? What is the speed of sound in each case? Speed of sound in air is 345 ms^(-1) .

A train is moving at a speed of 72 kmph towards a station sounding a whistle of frequency 640Hz. What is the apparent frequency of the whistle as heard by a man standing on the platform when train approaches towards him.

A train is approaching towards a platform with a speed of 10 m s^(-1) while blowing a whistle of frequency 340 Hz. What is the frequency of whistle heard by a stationary observer on the platform ? Given speed of sound = 340 ms^(-1) .

A train standing in a station yard, blows a whistle of frequency 400 Hz in still air. The wind starts blowing in the direction from the yard to the station with a s speed of 10ms^(-1) . What are the frequency , wavelength and speed of sound for an observer standing on the station's platform? Is the situation exactly identical to the case when the air is still and the observer runs towards the yard at a speed of 10 ms^(-1) ? The speed of sound in still can be taken as 340 ms^(-1)