Question

While sitting in your car by the side of a country road, you see your friend, who happens to have an identical car with an identical horn, approaching you. You blow your horn, which has a frequency of 260 Hz; your friend begins to blow his horn as well, and you hear a beat frequency of 6.0Hz .

How fast is your friend approaching you?

Express your answer to two significant figures and include the appropriate units.

Answer 1

`v_s =7.74\ m/s`

Step-by-step explanation:

given,

Speed of sound = 343 m/s

frequency of horn = 260 Hz

the friend is approaching, the frequency is increased by the Doppler Effect. The frequency is 266 Hz

using formula

`f' = (v)/(v-v_s)f_0`

`266= (343)/(343 - v_s)(260)`

`1.023= (343)/(343 - v_s)`

`343 - v_s = 335.26`

`v_s =7.74\ m/s`

the speed of friends approaching is equal to
`v_s =7.74\ m/s`