Answer:
The value is [tex]f_1 = 828 \ Hz[/tex]
Explanation:
From the question we are told that
The speed is [tex]v = 25 \ m/s[/tex]
The speed of the ambulance is [tex]u = 35 \ m/ s[/tex]
The frequency of the siren is [tex]f = 850 \ Hz[/tex]
Generally from Doppler effect equation we have that
[tex]f_1 = \frac{v_s - v }{ v_s + u } * f[/tex]
Here [tex]v_s[/tex] is the velocity of sound with the value [tex]v_s = 343 \ m/s[/tex]
=> [tex]f_1 = \frac{343 - 25 }{ 343 + 35 } * 850[/tex]
=> [tex]f_1 = 828 \ Hz[/tex]
