Question

A friend of yours is loudly singing a single note at 400 HzHz while racing toward you at 25.8 m/sm/s on a day when the speed of sound is 345 m/sm/s .

A.) What frequency do you hear?

B.) What frequency does your friend hear if you suddenly start singing at 400 HzHz ?

Answer 1

___________________________

frequency of source = n = 400Hz

speed of the source v_s = 25.8 m/s

speed of the sound   v = 345m/s

___________________________

(a)

using the doppler effect

when the source is moving towards the observer

n¹ = n* (v/v-v_s)

= 400*(345/(345-25.8))

= 432.3308 Hz

___________________________

(b)

inthe second case you becomes source

frequency source   n = 400Hz

menas observer moving towards you

   n¹ = n* (v+v₀)/v

    = 400*(345+25.8)/345

= 429.913 Hz

___________________________

Please rate

if any mistake in this answer please comment i will clarify your doubt . thank you