Answer:
The speed of the truck is 20.68 m/s.
Explanation:
Given that,
Frequency of horn = 211 Hz
Trucker hears a frequency = 187 Hz
Speed of sound = 343 m/s
Let the speed of the truck is [tex]v_{T}[/tex]
We need to calculate the speed of truck
Using Doppler shift
[tex]f = f_{0}\dfrac{v'-v_{0}}{v'+v_{s}}[/tex]
Where, [tex]f_{0}[/tex] = horn frequency
f = Trucker hears a frequency
v'=speed of sound
[tex]v_{0}[/tex] = speed of observer
v = speed of source
Put the value in to the formula
[tex]187=211\times(\dfrac{343+v_{T}}{343+v_{T}})[/tex]
[tex]v_{T}=\dfrac{211\times343-187\times343}{398}[/tex]
[tex]v_{T}=20.68\ m/s[/tex]
Hence, The speed of the truck is 20.68 m/s.