Question

As you stand by the side of the road, a car approaches you at a constant speed, sounding its horn, and you hear a frequency of 80.0 Hz. After the car goes by, you hear a frequency of 60.0 Hz. What is the speed of the car? The speed of sound in the air is 343 m/s.

Answer 1

Answer:

Speed of the car will be 49 m /sec

Explanation:

Speed of sound v = 343 m/sec

We have given that when car approaches he hears a sound of frequency 80 Hz

And when car go away from he hears a sound of frequency 60 Hz

So $80=\frac{f}{1-\frac{u}{v}}$

And $60=\frac{f}{1+\frac{u}{v}}$

So $80\times \left ( 1- \right\frac{u}{343} )=60\times \left ( 1- \right\frac{u}{343} )$

u = 49 m/sec