physics

posted by .

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 -

    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.

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. physics

    1)As a sound source moves away from a stationary observer, the number of waves will. decrease 2)How fast should a car move toward you for the car's horn to sound 2.88% higher in frequency than when the car is stationary?
  2. physics

    1)As a sound source moves away from a stationary observer, the number of waves will. decrease 2)How fast should a car move toward you for the car's horn to sound 2.88% higher in frequency than when the car is stationary?
  3. physics

    1)As a sound source moves away from a stationary observer, the number of waves will. A)increase B)decrease C)remain the same D)need to know the speed of the source (answer:decrease.) As the detector recedes from the source, the relative …
  4. Physics - Frequency

    While blowing its horn of frequency 580 Hz, a car accelerates at 0.4 m/s2. The car starts from rest by your side and moves away. How long will it take for the frequency you hear to decrease by 5%?
  5. Physics - Frequency

    This is in reply to a previous post, I'm not really sure whether replies to posts that are several days old are viewed by anyone, so I'm reposting just in case. In reply to bobpursley's post, I just want to ask, how would you know …
  6. Physics

    While blowing its horn of f=524 Hz a car accelerates at 0.8m/s^2 the car starts from rest by your side and moves away. Find the time it taked for the frequency you hear to decrease by 5%. Hint: Don't forget to include the time it takes …
  7. physics

    While blowing its horn of frequency 466 Hz, a car accelerates at 0.84 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%?
  8. PHYSICS

    A CAR IS TRAVELING AWAY FROM YOU AT 70.0 MI/H. THE CAR HORN PRODUCES A SOUND AT A FREQUENCY OF 5000HZ. WHAT FREQUENCY DO YOU HEAR?
  9. physics

    a car sounds its horn as it travels at a steady speed of 15m/s along a straight road between two observers x and y. the observer x heras a frequency of 538 hz while observer y hears a lower frequency. 1 is the car traveling towards …
  10. Physics

    Car A is 12 m ahead of car B on a straight stretch of road. Car A starts from rest and accelerates away from B at 4.0 m/s2. Two seconds later B starts from rest and accelerates after A at 6.0 m/s2. How long will it take B to catch …

More Similar Questions