Question

Two police car sirens have identical frequencies of 700Hz. Matthew on his bike which is at rest relative to the ground hears beats with a frequency of 18 beats/s when one car is approaching from one direction at 8.0 m/s. (I)What is the speed of the other car also moving towards him? (II)When both cars arrive in front of Patrick and stop, he realizes the police are going after him; he starts running away on his bike from both cars at 5m/s. If they are now chasing after him at their original speeds, how many beats per second would Matthew hear? Assume the speed of sound to be 343m/s.

Answer 1