posted by sammy .
At rest, a car’s horn sound at the note A(440Hz) The horn is sounded while the car is moving down the street. A bicyclist moving the same direction with one third the car’s speed hears a frequency of 415 Hz. What is the speed of the car? Is the cyclist adead of or behind the car?
The car is behind the cyclist, and moving closer, the pitch is higher.
use the speed of the source (car) as v, and that of the observer (moving away) as 1/3 v.
Use the doppler equatin. I will be happy to check your work.