An ambulance travels down a high way at a speed of 75.0 mi/h, its siren emitting

Question

An ambulance travels down a high way at a speed of 75.0 mi/h, its siren emitting sound at a frequency of 400 Hz. What frequency is heard by a passenger in a car travelling at 55.0 mi/h in the opposite direction as the car (a) approaches? (b) Moves away from the ambulance?

A train moving at a speed of 40.0 m/s sounds its whistle, which has a frequency of 500 Hz. Determine the frequency heard by a stationary observer as the train approaches the observer also find the frequency heard by the stationary observer as the train recedes from the observer.

Please show work.

Explanation / Answer

75 mi/h = 33.528 m/s

55 mi/h = 24.5872 m/s

speed of sound 340 m/s

part a )

approaches

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

vo = observer speed = car speed

vs = source speed

f = 400 Hz

f' = 475.85 Hz

part b )

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

f' = 337.766 Hz

part 2 )

here vo = 0

a)

approaches

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

f' = 566.67 Hz

part b )

recedes

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

f' = 447.368 Hz

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