Question

A hawk flying at 38 m/s emits a cry whose frequency is 440 Hz. A wren is moving in the same direction as the hawk at 17 m/s. (Assume the speed of sound is 343 m/s.) (a) What frequency does the wren hear (in Hz) as the hawk approaches the wren? Hz (b) What frequency does the wren hear (in Hz) after the hawk passes the wren?

Answer 1

Answer:

frequency wren hear when approaches is 470.29 Hz

frequency wren hear after hawk pass is 415.75 Hz

Explanation:

given data

hawk  velocity Vs= 38 m/s

frequency f = 440 Hz

wren velocity Vo= 17 m/s

speed of sound s = 343 m/s

to find out

What frequency wren hear and What frequency wren hear after hawk pass

solution

we apply here frequency formula that is

$f1=f ( \frac{s+V_o}{s+V_s} )$    .........1

here f1 is frequency hear by observer

put here all value as Vo and Vs negative because it approaches

$f1=f ( \frac{s-V_o}{s-V_s} )$  

$f1=440 ( \frac{343-17}{343-38} )$  

f1 = 470.29 Hz

so frequency wren hear when approaches is 470.29 Hz

and

after passing from equation 1 we take both Vo and Vs as positive

$f1=f ( \frac{s+V_o}{s+V_s} )$

$f1=440 ( \frac{343+17}{343+38} )$

f1 = 415.75 Hz

so frequency wren hear after hawk pass is 415.75 Hz