Home
Class 11
PHYSICS
A driver in a car , approaching a vert...

A driver in a car , approaching a vertical wall notices that the frequency of his car horn , has changed form 440 Hz to 480 Hz , when it gets reflected form the wall . If the speed of the sound in are 345 m/s , then the speed of the car is :

A

54 km/hr

B

36 km/hr

C

18 km/hr

D

24 km/hr

Text Solution

Verified by Experts

The correct Answer is:
A

`f_1` = Frequency heard by wall `= f_s = ((v_s)/(v_s-v_c))`
` f_2` = Frequency heard by driver after reflection from wall
`f_2=((v_s+v_c)/(v_s))f_1=((v_s+v_c)/(v_s-v_c))f_0`
`f_2/(f_0)=(v_s-v_c)/(v_s+v_c)implies (48)/44=(v_s-v_c)/(v_s+v_c)`
`12(v_s+v_c)=11(v_s-v_c)implies 23v_c=v_s`
`v_c = (v_s)/(23)=(345)/23 = 15 m//s`
`= (15 xx18)/5 = 54 ` km/hr
Promotional Banner

Similar Questions

Explore conceptually related problems

The driver of as car approaching a vertical wall notices that the frequency of his car's horn charges from 440 Hz to 480 Hz when it gets reflected from the wal. Find the speed of the car if that of the sound is 330 ms^-1 .

The driver of a car approaching a vertical wall notices that the frequency of the horn of his car changes from 400 Hz to 450 Hz after being reflected from the wall. Assuming speed of sound to be 340(m)/(s) , the speed of approach of car towards the wall is

The driver of a bus approaching a big wall botices that the frequency of his bus's horn changes from 420 Hz to 490 Hz when he hears it after it gets reflected from the wall. Find the speed of the bus if speed of the sound is "330 ms"^(-1) .

The frequency of a car horn encountered a change from 400 Hz to 500 Hz. When the car approaches a vertical wall. If the speed of sound is 330 m/s. Then the speed of car is ______ km/h.

A car, sounding a horn of frequency 1000 Hz, is moving directly towards a huge wall at a speed of 15 m/s. If speed of sound is 340 m/s, then the frequency of the echo heard by the driver is

A car is moving with a velocity of 5 m//s towards huge wall. The driver sounds a horn of frequency 165 Hz . If the speed of sound in air is 335 m//s , the number of beats heard per second by the driver is

A car sounding a horn of frequency 1000 Hz passes an observer. The ratio of frequencies of the horn noted by the observer before and after passing of the car is 11 : 9. If the speed of sound is v , the speed of the car is

A driver decreases the speed of a car from 25 m/s to 10 m/s is 5 seconds. Find the acceleration of the car.