Physics 112. Problems: The Doppler Effect

1. A car moving at 12 m/s sounds its 350 Hz horn as it approaches a stationary listener. If the Tair is 10⁰ C, what frequencies are heard by the listener?

2. A train moving at 19 m/s approaches a crossing signal with a 250 Hz bell. At 20⁰ C, a passenger on the train would hear what frequencies?

3. Your car is moving at 15 m/s toward another car approaching you at 10 m/s. The second car's horn is sounding 450 Hz. If the Tair is 5⁰ C, what pitches will you hear?

4. A truck sounding its 260 Hz horn approaches you at 15 m/s. If the Tair is 5⁰ C, what frequencies do you hear?

5. At 10⁰C, a car would be moving at what speed toward a listener standing on the sidewalk if she thinks its 320 Hz horn sounds like 346 Hz?

6. If the speed of sound in water is 1460 m/s, at what speed would a submarine be moving to reflect a 2 000 Hz sound pulse as 2 005 Hz?

7. A car moving at 14 m/s sounds its 356 Hz horn while following a lead car moving at 18 m/s. If the Tair is 20⁰ C, the occupants of the lead car will hear what frequency?

8. A referee blows her 4 000 Hz whistle as a hockey player skates toward her at 2 m/s. If the Tair is - 7⁰ C, what frequencies would be heard by the skater?

9. A bee whose wings buzz at 60 Hz, flies at 6 m/s toward a bear loping at 3 m/s toward its hive. If the Tair is 25⁰ C, what wing beat frequencies would the bear hear?

10. A model aircraft moving at 7 m/s emits a 7000 Hz engine whine as it approaches another model moving toward it at 9 m/s. If the Tair is - 15⁰ C, what frequencies would reach the second model?

11. A car moving at 16 m/s sounds its 270 Hz horn as it approaches a listener walking away from it at 0.7 m/s. If the Tair is 16⁰ C, what frequencies are heard by the listener?

12. A train approaches a crossing at 11 m/s sounds its 300 Hz horn. At 20⁰ C, a person standing by the crossing would hear what frequencies?

13. Two cars travel down the highway. The rear car moves at 7 m/s and sounds its 400 Hz horn. The lead car moves at 4 m/s. If the Tair is 20⁰ C, the occupants of the lead car will hear what frequencies?

14. You are jogging away from a parked truck at 1.3 m/s. If the truck's horn sounds at 160 Hz horn, what frequency do you hear in 5⁰ C air?

15. A lion running at 6.3 m/s chases a gazelle bleating at 650 Hz as it runs away at 4.6 m/s. If the Tair is 38⁰ C, what frequencies does the lion hear? (The prey dodges and the lion runs past.)