Two trains are traveling toward each other at 30.5 m/s relative to the ground. O
ID: 1747843 • Letter: T
Question
Two trains are traveling toward each other at 30.5 m/s relative to the ground. One train is blowinga whistle at 1060 Hz. (a) What frequency will be heard on the othertrain in still air?1 Hz
(b) What frequency will be heard on the other train if the wind isblowing at 30.5 m/s toward the whistle andaway from the listener?
2 Hz
(c) What frequency will be heard if the wind direction isreversed?
3 Hz
Section 17-9 The Doppler Effect (a) What frequency will be heard on the othertrain in still air?
1 Hz
(b) What frequency will be heard on the other train if the wind isblowing at 30.5 m/s toward the whistle andaway from the listener?
2 Hz
(c) What frequency will be heard if the wind direction isreversed?
3 Hz
Section 17-9 The Doppler Effect
Explanation / Answer
Given frequency f = 1060Hz v = 343 m/s Two trains are traveling toward each other at 30.5 m/s relative to the ground a) the frequency heard in still air is f ' =f(v+vD/v-vS) =(1060Hz)(343+30.5/343-30.5) =---------Hz b) In a frame of reference where the air seems still , thevelocity of the detector is vD = 30.5 -30.5 = 0, andthat of the source is vS = 2(30.5) therefore f ' = f(v+vD/v-vS) =(1060Hz){343+0/343-2(30.5)} =---------Hz c) we again pick a frame of reference where the airseems still . Now , the velocity of the source is vS =30.5-30.5=0, and that of the detector is vD = 2(30.5) therefore f ' = f(v+vD/v-vS) =(1060Hz){343+2(30.5)/343-0} =---------Hz =(1060Hz){343+0/343-2(30.5)} =---------Hz c) we again pick a frame of reference where the airseems still . Now , the velocity of the source is vS =30.5-30.5=0, and that of the detector is vD = 2(30.5) therefore f ' = f(v+vD/v-vS) =(1060Hz){343+2(30.5)/343-0} =---------Hz =(1060Hz){343+2(30.5)/343-0} =---------HzRelated Questions
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