An ambulance moving at 38 ms sounds its siren whose frequenc

An ambulance moving at 38 m/s sounds its siren whose frequency is 380 Hz. A car is moving in the same direction as the ambulance at 22 m/s.

(a) What frequency does a person in the car hear as the ambulance approaches the car? Hz

(b) What frequency does a person in the car hear after the ambulance passes the car? Hz

Solution

velocity of sound source(ambulance), vs = 38 m/s

f = 380 hz

velocity of obsorver(car), vo = 22 m/s

we know, velocity of sound, v = 340 m/s

a) The frequency does a person in the car hear as the ambulance approaches the car,

f\' = f*(v - vo)/(v - vs)

= 380*(340 - 22)/(340 - 38)

= 400.13 Hz

b) The frequency does a person in the car hear after the ambulance passes the car,

f\'\' = f*(v + vo)/(v + vs)

= 380*(340 + 22)/(340 +38)

= 363.91 Hz