Homework Help: physics

Posted by OMAR on Monday, May 30, 2011 at 1:41pm.

a car, moving at 100 mi/hr, passes a stationary police car whose siren has a frequency of 500 Hz. what is the frequency change heard by observer in the moving car as he passes the police car? the velocity of sound in air is 343 m/s. ( 1 mi= 1.609 km).
answer in units of Hz.

physics - Henry, Tuesday, May 31, 2011 at 4:18pm
Vr=100mi/h * 1609m/mi * (1h/3600s)=44.69m/s.

F = ((V-Vr)/(V+Vs))*Fo.
F=((343-44.69) / (343+0))*500 = 434.9Hz

Change = 500 - 433.9 = 65.1Hz.

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