Answer:
Explanation:
Given
Apparent frequency [tex]f'=1370\ Hz[/tex]
Velocity of sound [tex]v=343\ m/s[/tex]
speed of observer [tex]v_o=35\ m/s[/tex]
Using Doppler effect Apparent frequency when source is approaching is given by
[tex]f'=f(\frac{v-v_0}{v-v_s})[/tex]
[tex]1370=f(\frac{343-35}{343-v_s})---1[/tex]
Apparent frequency when source moves away from observer
[tex]f''=f(\frac{v+v_0}{v+v_s})[/tex]
[tex]1330=f(\frac{343+35}{343+v_s})---2[/tex]
Divide 1 and 2 we get
[tex]\frac{f'}{f''}=\frac{\frac{343-35}{343-v_s}}{\frac{343+35}{343+v_s}}[/tex]
[tex]\frac{1370}{1330}=\frac{343-35}{343-v_s}\times \frac{343+v_s}{343+35}[/tex]
[tex]v_s=40\ m/s[/tex]
Thus speed of sound of police car is 40 m/s
