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The Doppler Formula. Una ricorsa per il CLIL di Fisica in lingua inglese

red - Di seguito viene proposta un'attività sull'effetto Doppler, utile per le classi in cui sono attivi dei percorsi CLIL di Fisica in lingua inglese.

The Doppler Formula

For each of the situations given, indicate:

a) how the motion of the source affects the frequency heard by the observer. (raises, lowers, no effect)

b) how the motion of the observer affects the frequency heard by the observer.

c) the answer to the question. Make sure to show your work.

Assume the speed of sound is 331.0 m/s unless you are told otherwise.

1) Jenny is standing at the railroad crossing; an oncoming train blows its whistle at 1520. Hz as it approaches at a speed of 34.5 m/s. What frequency does Jenny hear?

2) The Jamaican bobsled team is practicing in front of their fans. As they pass by on their way down the track, a young fan standing there blows a bugle at a frequency of 880. Hz. What frequency do the bobsledders hear after they have passed the young musician if they are traveling at 41.7 m/s?

3) If I shoot a bottle rocket away from me at a speed of 43.4 m/s and I hear a frequency of 2520 Hz, What is the actual frequency of the bottle rocket’s whistle when the air temperature is 24.0˚C.

4) A  school bus and tour bus are approaching each other on the highway. The drivers both greet each other by honking the horns, which both vibrate at 1250 Hz.

  • If the school bus is moving at a rate of 15.7 m/s and the tour bus is moving at 29.9 m/s, what frequency does the driver of the tour bus hear?
  • What frequency does the school bus driver in the problem above hear?

5) On a nice, 19.6˚C day, a bully trips Ryan and speeds away on his old squeaky scooter. As Ryan runs after the bully at a rate of 6.75 m/s, he hears the scooter squeaking at a frequency of 675 Hz. If the actual frequency of the scooter’s squeak is 700. Hz, how fast is the bully moving?

6) In a high speed pursuit, the chasing officer turns on the siren, which malfunctions and sticks on a steady 2325 Hz scream. The culprit being pursued hears the siren at a tone of 2376 Hz. If the officer’s vehicle is travelling at 38.75 m/s and is closing the distance to the fleeing culprit at a rate of 6.870 meters every second, what is the air temperature?

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