- #1
mastermind1
- 12
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A kid is riding a bike and is ringing bell of 3000 Hz. You are standing still on the sidewalk.When the bicycle moves toward you, you hear a shift in the frequency of the bell. In addition, when the bicycle moves away from you, you hear a different shift in the frequency of the bell. If there is a 30 Hz change in the frequencies that you hear for the bell as the bicycle approaches you and then moves away from you, what is the speed (in m/s) of the bicycle? (Write your answer to the nearest 0.01 m/s.)
1. Homework Statement
Frequency(source)(fs) = 3000 Hz
speed(observer)(vo) = 0 m/s
Frequency(towards)(ft)= 3030 Hz (NOT SURE)
Frequency(away)(fa) = 2970 Hz (NOT SURE)
speed of sound(v) = 343 m/s
fo = ((v+vo)/(v-vs)) * fs Bike is moving TOWARDS me
fo = ((v-vo)/(v+vs)) * fs Bike is moving AWAY from me
Towards
------------
3030Hz/3000Hz = (343 m/s) / (343 m/s - vs)
(1.01)(343 m/s - vs) = 343 m/s
345.20 m/s - 1.01 vs = 343 m/s
vs = 2.18 m/s
I do the same thing using the AWAY equation, and i get the same answer.
However, that answer is incorrect. I do not know what I am doing wrong.
1. Homework Statement
Frequency(source)(fs) = 3000 Hz
speed(observer)(vo) = 0 m/s
Frequency(towards)(ft)= 3030 Hz (NOT SURE)
Frequency(away)(fa) = 2970 Hz (NOT SURE)
speed of sound(v) = 343 m/s
Homework Equations
fo = ((v+vo)/(v-vs)) * fs Bike is moving TOWARDS me
fo = ((v-vo)/(v+vs)) * fs Bike is moving AWAY from me
The Attempt at a Solution
Towards
------------
3030Hz/3000Hz = (343 m/s) / (343 m/s - vs)
(1.01)(343 m/s - vs) = 343 m/s
345.20 m/s - 1.01 vs = 343 m/s
vs = 2.18 m/s
I do the same thing using the AWAY equation, and i get the same answer.
However, that answer is incorrect. I do not know what I am doing wrong.