A police car, parked by the roadside, sounds its siren, which has a frequency f of 1000 Hz. What frequency f ′ do you hear if
(a) you are driving directly toward the police car at 30 m s–1?
(b) you are driving away from the police car at the same speed?
(c) you are at rest and the police car is coming toward you at 30 m s–1?
(d) you are at rest and the police car is going away from you at the same speed?
(e) both you and the police car are driving toward each other at 30 m s–1?
(f) both you and the police car are driving away from each other at 30 m s–1?
