Home
Class 12
PHYSICS
A train is moving on a straight track wi...

A train is moving on a straight track with speed 20 `ms^(-1)`. It is blowing its whistle at the frequency of 1000 Hz. The percentage change in the frequency heard by a person standing near the track as the train passes him is (speed of sound = 320 `ms^(-1)` ) close to :

A

`12%`

B

0.18

C

0.24

D

0.06

Text Solution

Verified by Experts

The correct Answer is:
A
`f_(1) = f [ (v)/(v-v_(2)) ] = f [ (320)/(320 - 20) ] = f xx (320)/(300) `Hz
` f_(2) = f [ (v)/(v + v_(s)) ] = f xx (320)/(340)` Hz
100 `xx (f_(2)/(f_(1)) - 1) = ((f_(2) - f_(1))/(f_(1))) xx 100 `
= 100` [(300)/(340) - 1 ] ` = 12 %
So correct choice is a.
Promotional Banner

Topper's Solved these Questions

  • WAVE MOTION

    MODERN PUBLICATION|Exercise RECENT COMPETITIVE QUESTIONS|18 Videos

  • WAVE MOTION

    MODERN PUBLICATION|Exercise MULTIPLE CHOICE QUESTIONS (LEVEL -II)|73 Videos

  • UNITS, MEASURMENTS, DIMENSIONS, ERRORS OF MEASUREMENTS

    MODERN PUBLICATION|Exercise Recent Competitive Questions|7 Videos

  • WAVE OPTICS

    MODERN PUBLICATION|Exercise Recent Competitive Questions|18 Videos

Similar Questions

Explore conceptually related problems

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 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 car sounding its horn at 480 Hz moves towards a high wall at a speed of 20 ms^-1 . If the speed of sound is 340 ms^-1 , the frequency of the reflected sound heard by the passenger sitting in the car will be nearest to

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) ?

A source of sound is moving with a velocity of 50ms^(-1) towards a stationary observer . The Observer measure the frequency of sound as 500Hz. The appartment frequency of sound as heard by the observer when source is moving away from hom with the same speed is (Speed of sound at room temperature 350ms^(-1)