U.2
HyUCHLICS ULLSC
9. While standing near a railroad crossing, a person hears a distant train hom. According to the train's
engineer, the frequency emitted by the horn is 440 Hz.
a) What would be the frequency heard by the person if the train were at rest?
b) What would be the frequency that reaches the bystander as the train approaches the crossing?
e) What would be the frequency that reaches the bystander once the train has passed the crossing?
10. An alarm clock is dropped off the edge of a tall building. You, standing directly under it, hear a tone of
1350 Hz coming from the clock just before you duck out of the way and it hits the ground. Would the actual
frequency of the clock be higher or lower than what you heard?
11. Two identical cars are driving toward one another and sounding their horns. You're the driver of one of
the cars. You measure your car's horn to be sounding at 512 Hz, but you measure the horn of the other car to
be sounding at 600. Hz. Are these measurements reasonable? Why?