Question

A stationary police car emits a sound of frequency 1200 Hz that bounces off of a car on the highway and returns with a frequency of 1230 Hz . The police car is right next to the highway, so the moving car is traveling directly toward or away from it. Part A How fast was the moving car going?

What frequency would the police car have received if it had been traveling toward the other car at 17.0 m/sm/s ?

Express your answer in hertz.

Answer 1

PART A:

Let " V" be the speed of the car.

(u + v) / (u-v) = f₂ / f_o

(u + v) / (u-v) = (1230) / (1200)

(343 + v) / (343-v) = 1.025

V = 4.23 m/s --------------- (**Answer**)

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PART B:

Frequency police car receives will be:

f₂ = f_o [(u + v)/(u-v)] x [(u+v_p) / (u - v_p) ]

f₂ = 1200 x [1.025] x [ (343 + 17) / (343-17)]

f₂ = 1200 x [1.025] x [1.10429]

f₂ = 1358 Hz --------------- (**Answer**)

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