Look at the energy bar graph on the left. The total energy does not move, as it shows the maximum energy used or stored at any given instant. However, the potential energy and kinetic energy are constantly changing. Why?

(a): The moving car was going at Vo= 14.29 m/s moving toward the police car.

(b) If the police car had been traveling toward the other car at 20 m/s would receive a frequency of f''= 1327.39 Hz.

Explanation:

V= 343 m/s

f= 1200 Hz

f'= 1250 Hz

Vo= ?

Vf= 0

f'= f* {(V - (Vo) / V}

clearing Vo:

Vo= 14.29 m/s  (a)

f''= f* {(V - (Vo) / V - 20 m/s}

f''= 1327.39 m/s (b)