Q1.

A car moving at 35 m/s passes a stationary police car whose siren has a frequency of 730 hz. What is the change in the frequency (in Hz) heard by an observer in the moving car as he passes the police car? (The speed of sound in air is 343 m/s.)

Q2.

A truck is moving at 26m/s, and a police car is moving at 45 m/s in the opposite direction. If the frequency of the siren emitted by the police car is 722 Hz, what is the frequency heard by an observer in the truck as the police car approaches the truck? (The speed of sound in air is 343 m/s.)