Question

I need some help w/ this:

A police car siren emits a frequency of 2010 Hz when stationary. When it is driving toward a stationary car, the other driver hears a frequency of 2120 Hz. How fast is the police car driving?


Using the doppler's effect equation, I got the answer ±16.3, but that apparently isn't the correct answer.

Edited: Ohhh Ok, I got it, answer is 17.7 ... whoops

Answer 1

17.798

Step-by-step explanation:

Acellus

Answer 2

The velocity of the police car is, v = 17.798 m/s

Step-by-step explanation:

Given data,

The actual frequency of the siren, f = 2010 Hz

The observed frequency of siren is, f' = 2120 Hz

The velocity of the observer, v' = 0 m/s

The velocity of the source, v = ?

The formula for Doppler effect,

`f'=((V+v'))/((V-v))f`

Where,

V - velocity of sound waves in air.

`v=V-(V+v')(f)/(f')`

Substituting the given values,

`v=343-(343+0)(2010)/(2120)`

v = 17.798 m/s

Hence, the velocity of the police car is, v = 17.798 m/s