1. The problem statement, all variables and given/known data You are driving along a highway at 27.5 m/s when you hear the siren of a police car approaching you from behind and you perceive the frequency as 1250 Hz. You are relieved that he is in pursuit of a different speeder when he continues past you, but now you perceive the frequency as 1202 Hz. What is the speed of the police car? The speed of sound in air is 343 m/s. So, U_o= 27.5 m/s U_s = ?? v= 343 m/s 2. Relevant equations It states that the perceived frequency from behind is 1250 ad the 1202 after it is gone by 3. The attempt at a solution I used the equation f ' =(1+- u_o/v)/(1+-u_s/v)f Because it gives you information when the car is behind you and then after it has passed you I used two equations and let them equal each other but I am unsure if the perceived frequencies are f or f ' ??