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April 19, 2014

April 19, 2014

Posted by **itufizik** on Monday, July 16, 2012 at 4:57pm.

a) How fast was the police car moving?

b) You are so nervous after the police car passes you that you pull off the road and stop. Then you hear another siren, this time from an ambulance approaching from behind. The frequency of its siren that you hear is 1880. Hz. Once it passes, the frequency is 1680. Hz. What is the actual frequency of the ambulance’s siren?

- physical -
**Henry**, Tuesday, July 17, 2012 at 8:48pm((V+Vr)/(V+Vs))*Fs = 1760 Hz.

V = 343m/s = Velocity of sound in air.

Vr=27.7m/s=Velocity of receiver(motorist).

Vs = Velocity of source(Police car).

a. ((343+27.7)/(343+Vs))1830 = 1760

((370.7)/(343+Vs))1830 = 1760

678381/(343+Vs) = 1760

Cross multiply:

1760((343+Vs) = 678,381

343 + Vs = 385.44

Vs = 385.44 - 343 = 42.4 m/s = Velocity

of police car.

b. F = (1880+1680) /2 = 1780 Hz.

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