A car moving at 142 mi/hr passes a station-
ary police car whose siren has a frequency of
500 Hz.
The velocity of sound in air is 343 m/s.
What is the frequency change heard by an
observer in the moving car as he passes the
police car (i.e., the difference between the
frequency heard as the observer approaches
the police car and the one heard as he is
moving away from the police car)? (1 mi =
1.609 km)
Answer in units of Hz