In each of the four scenarios to the right, a large bat lets out a short burst o

Question

In each of the four scenarios to the right, a large bat lets out a short burst of ultrasonic sound, which the smaller bat hears a moment later. If the large bat flies at 13.40 m/s and the small bat flies at 2.650 m/s, rank the frequency that the smaller bat detects in the four scenarios, from highest to lowest. Assume that the speed of sound is 343.0 m/s highest frequency lowest frequency C B AD In scenario C, some of the large bat's signal reflects off of the small bat and returns to the large bat, warning it of the smaller bat's presence. If the initial signal has a frequency of 61.40 kHz, what return frequency will the large bat detect? Calculate the final frequency to four significant figures C Number kHz

Explanation / Answer

from doppler effect

F = Fo*(V + Vr)/(V + Vs)

(a)

Vr +ve if receiver moving toward source ; Vs -ve if source moving toward receiver.

A. F = Fo*(343-13.40) / (343-2.650) = 0.968*Fo

B.   F = Fo*(343-13.40) / (343+2.650) = 0.953*Fo

C.  F = Fo*(343+13.40) / (343-2.650) = 1.047*Fo

D.  F = Fo*(343+13.40) / (343+2.650) = 1.031*Fo

Frequency from hightest to lowest is

C,D,A,B

(b)

frequency heard by the small bat is scenario c is

        f ' = f (V + Vr) / (V- Vs)

f' = (61.40 kHz) (343 + 2.650) / (343 - 13.40) =

f' = 64.38 kHz

The reflected wave heard by the large bat is

          f '' = f ' (V+ Vr) / (V- Vs)

f" = (64.38 kHz)(343 + 13.40) / (343 - 2.650)

f" = 67.41 kHz

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