Atrain traveling 80.0 kph is blowing its horn as it approaches a railroad crossing. the horn has a frequency of 300.0 hz. assume the speed of sound is 331.5 m/s. what is the observed frequency of the horn?

395 hz

281 hz

322 hz

322 Hz

Explanation:

v = speed of train approaching the railroad crossing = 80 km/h = 80 x 1000/3600 m/s = 22.22 m/s

V = speed of sound of the horn of train = 331.5 m/s

f = actual frequency of the sound from the horn = 300.0 Hz

f' = observed frequency of the horn

Using Doppler's effect, observed frequency is given as

f' = V f/(V - v)

inserting the values

f' = (331.5) (300.0)/(331.5 - 22.22)

f' = 322 Hz