Two cars are approaching each other on a straight road and moving with a velocity 60 Kmph. If the sound produced in one car is of frequency 500Hz. What will be the frequency of sound as heard by a person sitting in another car. When
the car has crossed and moving away from each other, what will be the frequency of sound as heard by the same person. (speed of sound in air is 332 ms-').
plzz answer this question, it's urgent
Answers
The frequency heard when cars are approaching each other = 552.86 Hz
The frequency heard the cars have crossed each other = 452.19 Hz
f = frequency of the sound produced by one car = 500 Hz
f' = frequency of sound heard by other car when both the cars are approaching each other
Given the velocity of both the cars = 60 Km/h = 16.67 m/s
Using the Doppler's effect equation to find the value of f'
f' = f (velocity of sound w.r.t listener / velocity of sound w.r.t to source)
velocity w.r.t listener = speed of sound in air + speed of car
= 332 + 16.67 = 348.67 m/s
velocity w.r.t source = speed of sound in air - speed of car
= 332 - 16.67 = 315.33 m/s
f' = 500(348.67/315.33)
=> f' = 552.86 Hz
Let f'' be the frequency of sound heard by the other car when the cars have crossed each other .
Using the Doppler's effect equation to find the value of f''
f'' = f (velocity of sound w.r.t listener / velocity of sound w.r.t to source)
velocity w.r.t listener = speed of sound in air - speed of car
= 332 - 16.67 = 315.33 m/s
velocity w.r.t source = speed of sound in air + speed of car
= 332 + 16.67 = 348.67 m/s
f'' = 500(315.33/348.67)
=> f' = 452.19 Hz