(a) What frequency is received by a person watching an oncoming ambulance moving
ID: 1532830 • Letter: #
Question
(a) What frequency is received by a person watching an oncoming ambulance moving at 31.9 m/s and emitting a steady 753 Hz sound from its siren? The speed of sound on this day is 345 m/s.
___________Hz
(b) What frequency does she receive after the ambulance has passed?
______________ Hz
A light-rail commuter train blows its 200 Hz horn as it approaches a crossing. The speed of sound is 339 m/s.
(c) An observer waiting at the crossing receives a frequency of 214 Hz. What is the speed of the train?
___________ m/s
(d) What frequency does the observer receive as the train moves away?
___________Hz
Explanation / Answer
Doppler effect for a moving source and stationary observer: f = fV/(V±Vs)
Vs = 31.9 m/s ,V = 345 m/s, f = 753 Hz
a) Moving towards: f = fV/(V–Vs)
f = 829.72 Hz
b) Moving away: f = fV/(V+Vs)
f = 689.268Hz
2.
(a) fd=f(v+vr)/(v-vs) , (fd=214Hz , f=200Hz , v=339m/s , vr=0)
214= 200*(339+0)/(339-vs)
vs= 22.17[m/s] approx.
(b) fd=f(v+vr)/(v+vs) , (f=200Hz , v=339m/s , vr=0 , vs=22.17m/s)
fd= 200*(335+0)/(335+22.17)= 187.586 = 187.6[Hz] approx.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.