Posted by PLEASE HELP!! on Thursday, February 3, 2011 at 8:58pm.
While blowing its horn of frequency 477 Hz, a car accelerates at 0.94 m/s2.
The car starts from rest by your side and moves away.
How many seconds does it take for the frequency you hear to decrease by 5%?
Hint: Do not forget to include the time it will take for sound to reach you.
*Im getting an answer of about 20, but i don't want to submit my homework yet, can someone please check it over to see if i am correct?*

physics  Henry, Sunday, February 6, 2011 at 12:23pm
F = ((V + Vr) / (V + Vs))Fo = 0.95*477.
((343 + 0) / (343 + Vs))477 = 453.15,
(343 / (343 + Vs))477 = 453.15 Hz,
163611 / (343 + Vs) = 453.15,
Cross multiply:
155430.45 + 453.15Vs = 163611
453.15Vs=163611  155430.45 = 8180.55,
Vs = 8180.55 / 453.15 = 18.05m/s.
Vf = Vi + at = 18.05m/s.
0 + 0.94t = 18.05,
t = 18.05 / 0.94 = 19.2s to reach final velocity.
d = Vi*t + 0.5at^2,
d = 0*19.2 + 0.5 * 0.94 * (19.2)^2,
d = 0 + 173.26m = 173.2m after final velocity.
d = V*t,
t = d / V = 173.2m / 343m/s = 0.50s to
reach receiver(you).
t(tot.) = 19.2 + 0.5 = 19.7s
So our answers are about the same.
Answer This Question
Related Questions
 physics  While blowing its horn of frequency 466 Hz, a car accelerates at 0.84 ...
 Physics  Frequency  While blowing its horn of frequency 580 Hz, a car ...
 Physics  While blowing its horn of f=524 Hz a car accelerates at 0.8m/s^2 the ...
 Physics  Frequency  This is in reply to a previous post, I'm not really sure ...
 physics  1)As a sound source moves away from a stationary observer, the number ...
 physics  1)As a sound source moves away from a stationary observer, the number ...
 physics  1)As a sound source moves away from a stationary observer, the number ...
 physics  a car sounds its horn as it travels at a steady speed of 15m/s along a...
 PHYSICS  A CAR IS TRAVELING AWAY FROM YOU AT 70.0 MI/H. THE CAR HORN PRODUCES A...
 Physics  Car A is 12 m ahead of car B on a straight stretch of road. Car A ...
More Related Questions