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allsm [11]
3 years ago
12

A train is traveling away from you at 120 km/h. it blows its whistle, and you hear a tone of 0.400 kHz. Take the speed of sound

to be 340 m/s. What frequency does the whistle actually produce? A) 444 Hz. B) 439 Hz C) 364 Hz D) 361 Hz
Physics
1 answer:
Vaselesa [24]3 years ago
5 0

Answer:B)439.21 Hz

Explanation:

Given

velocity of train v=120 km/h\approx 120\times \frac{5}{18}=33.33 m/s

frequency of train f_a=0.400 kHz\approx 400 Hz

speed of sound c=340 m/s

frequency from Doppler effect can be calculated by

f_a=(\frac{c}{c+v})\cdot f

400=(\frac{340}{340+33.33})\cdot f

400=\frac{340}{373.33}\cdot f

f=400\times 1.098

f=439.21 Hz

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