a flying bat emits squeaks of frequency 80 kHz.if a stationary observer hears the frequency of the squeaks as 78kHz,is the bat moving towards or away from the observer?determine the speed at which the bat is flying.

Answer 1

away of course

in general for non-relativistic Doppler effect

f heard = f emmitted (c+vr)/(c+vs)
c = v of wave
vr = v receiver (plus if toward source)
vs = v source, (plus if source moving away from receiver)

use your c of sound
78 = 80 (c+0)/(c+vs)

Answer 2

given:
fl = 78kHZ
Fs = 80kHz
vl = o (stationary)
vs =?
v =340 m.s-1

fl =v-vl/v+vs•Fs
78 =340-0/340+vs x80
therefore vs=8.72 m.s-1