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(8%) Problem 5: You are standing on a train station platform as a train goes by close to you. As the train approaches, you hear the whistle sound at a frequency of/,-98 Hz. As the train recedes, you hear the whistle sound at a frequency of fi- 78 Hz. Take the speed of sound in air to be v 340 m/s Randomized Variables f 98 Hz f2 78 Hz > ? 25% Part (a) Find an equation for the speed of the sound source vs. in this case it is the speed of the train. Express your answer in terms of fi,f2, andv Grade Summary Deductions Potential 0% 100% Submissions Attempts remaining: 7 (3% per attempt) detailed view Im Submit Hint I give up! Hints: 0% deduction per hint. Hints remaining: 2 Feedback: 0% deduction per feedback. 25% Part (b) Find the numeric value, in meters per second, for the speed of the train. 25% Part (c) Find an equation for the frequency of the train whistle S (\"s is for source ) that you would hear if the train were not moving. Express your answer in terms of f?,f2, and v 25% Part d) Find the numeric value in hertz, for the frequency of the train whistle s that you would hear if the train were not moving
Solution
when source moving towards the observer
f1 = ((v/ (v-v s )) * f s
where vs is velocity of source and fs is frequency of source
in given problem f 1 is given as 98 Hz and v = 340 m/sec
98 = ((340/(340-v s )) * f s
340 f s + 98 v s = 340*98
340 f s + 98 v s = 33320 .... (1)
2. when source move away from observer
f2 = ((v/(v+v s )) *f s
78 = ((340/ (340+v s ))* f s
340 f s -78 v s = 26520 .... (2)
by solving 1 abd 2
we will get v s = 38.7 m/sec
and f s = 86.9 Hz
.

(8%) Problem 5: You are standing on a train station platform as a train goes by close to you. As the train approaches, you hear the whistle sound at a frequency of/,-98 Hz. As the train recedes, you hear the whistle sound at a frequency of fi- 78 Hz. Take the speed of sound in air to be v 340 m/s Randomized Variables f 98 Hz f2 78 Hz > ? 25% Part (a) Find an equation for the speed of the sound source vs. in this case it is the speed of the train. Express your answer in terms of fi,f2, andv Grade Summary Deductions Potential 0% 100% Submissions Attempts remaining: 7 (3% per attempt) detailed view Im Submit Hint I give up! Hints: 0% deduction per hint. Hints remaining: 2 Feedback: 0% deduction per feedback. 25% Part (b) Find the numeric value, in meters per second, for the speed of the train. 25% Part (c) Find an equation for the frequency of the train whistle S (\"s is for source ) that you would hear if the train were not moving. Express your answer in terms of f?,f2, and v 25% Part d) Find the numeric value in hertz, for the frequency of the train whistle s that you would hear if the train were not moving
Solution
when source moving towards the observer
f1 = ((v/ (v-v s )) * f s
where vs is velocity of source and fs is frequency of source
in given problem f 1 is given as 98 Hz and v = 340 m/sec
98 = ((340/(340-v s )) * f s
340 f s + 98 v s = 340*98
340 f s + 98 v s = 33320 .... (1)
2. when source move away from observer
f2 = ((v/(v+v s )) *f s
78 = ((340/ (340+v s ))* f s
340 f s -78 v s = 26520 .... (2)
by solving 1 abd 2
we will get v s = 38.7 m/sec
and f s = 86.9 Hz
.

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