physics

posted by .

A bat flying at 5.0 m/s emits a chirp at 35 kHz. If this sound pulse is reflected by a wall, what is the frequency of the echo received by the bat?

I keep getting the wrong answer, don't understand.

  • physics -

    The answer depends upon whether the bat is flying towards the wall or away from it (or parallel to it). The problem should have stated which it is.

    If flying away or towards the wall, there are TWO Doppler shifts involved. The wall "receives" and reflects a Doppler-shifted sound, and when the bat hears it, it is shifted again.

  • physics -

    Do you need a numerical answer? If the bat is flying towards the wall,
    f' = f*[V+Vs) / V]
    f' = unknown, f = 35 kHz, V = 343 m/s (in dry air, 20 deg C), Vs = (5.0*2 = 10 m/s) <--Based on drwls</> suggestion, the source moves with a velocity of 5.0 m/s toward the wall, but then the bat continues to move at 5.0 m/s toward the reflected waves, doubling the speed between bat the source</> and bat the observer to 10 m/s </>.

    If the bat is flying away from the wall,
    f' = f*[V-Vs) / V]. Use the same values as above.

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. physics

    A bat flying at 5.5 m/s emits a chirp at 35 kHz. If this sound pulse is reflected by a wall, what is the frequency of the echo received by the bat?
  2. physics

    A bat flying at 6.00 m/s emits a chirp at 40.0 kHz. If this sound pulse is reflected by an insect moving away from the bat at 2.00 m/s, what is the frequency of the echo received by the bat?
  3. physics

    1.calculate th speed of waves in water that are 0.4m apart and have a frequency of 2hz?
  4. PHYSICS

    A bat flies toward a wall at a speed of 3.5 m/s. As it flies, the bat emits an ultrasonic sound wave with frequency 30.5 kHz. What frequency does the bat hear in the reflected wave?
  5. university physics

    A bat flying toward a wall at a speed of 6.47 m/s emits an ultrasound wave with a frequency of 27.5 kHz. What frequency does the reflected wave have when it reaches the flying bat?
  6. physics please help!

    A bat moving at 6.5 m/s is chasing a flying insect. The bat emits a 37 kHz chirp and receives back an echo at 37.65 kHz. At what speed is the bat gaining on its prey?
  7. physics

    A bat moving at 3.7 m/s is chasing a flying insect. The bat emits a 36 kHz chirp and receives back an echo at 36.79 kHz. At what speed is the bat gaining on its prey?
  8. physics

    A bat flying at 4.54 m/s emits a chirp at 115 kHz. If the pulse is reflected by a wall, what is the frequency (kHz) of the echo heard by the bat?
  9. science

    A bat moving at 5.6 m/s is chasing a flying insect. The bat emits a 60 kHz chirp and receives back an echo at 60.63 kHz. At what speed is the bat gaining on its prey?
  10. Physics

    A bat moving at 5 meters per second is chasing a flying insect, if the bat emits a 40 khz chirp and receives back an echo at 40.4 khz what is the speed of the insect and will the bat be able to catch the insect?

More Similar Questions