The speed of the fetal heart wall at the instant is 0.031 m/s when 72 beats per second of hart beat was detected.
The Doppler Effect, defined as the change in frequency of a wave in relation to an observer moving relative to the wave source, must be used.
Let
v= magnitude of the heart wall speed
V= speed  of sound = 1500
fh= the frequency the heart receives (and  reflects) =
fi= original frequency
ff= reflected frequency
fb= frequency for the beats=72
Make use of the Doppler Effect formula.
We have this formula because the heart is a moving observer and the device is a stationary source.
[tex]f_h = [(V+ v)/(v)] fi....(1)[/tex]
We can use this formula if we consider the heart to be a moving source and the device to be a stationary observer.
[tex]f_f = [(V)/(V-v)] fh....(2)[/tex]
The beats' frequency would be the difference between the original and reflected frequencies.
[tex]f_b = f_f -f_i......(3)[/tex]
substituting (1) and (2) into (3),
[tex]f_b=\frac{V}{V-v}\frac{V+v}{V}f_i-f_i\\\\f_b=f_i(\frac{V+v}{V-v}-1)\\\\f_b=f_i\frac{V+v-V+v}{V-v}\\\\f_b=\frac{2v}{V-v}[/tex]
solving for v ,
[tex]v=V\frac{f_b}{2f_i-f_b}=1500\frac{72}{2(1.70*10^6)-72}=0.031 m/s[/tex]
Thus, the speed of fetal heart is 0.031 m/s
To learn more about doppler effect refer here
https://brainly.com/question/15318474
#SPJ4
