Doppler Effect and Sound Frequency

The video tutorial explains a physics problem involving a train with a piano playing the A4 key (440 Hz) as it approaches an observer. Due to the Doppler effect, the observer hears a higher frequency, specifically a B note (494 Hz). The tutorial walks through the algebraic steps to determine the speed at which the train must travel for this frequency shift to occur, using the known speed of sound (343 m/s). The final calculation shows that the train must move at 37.5 m/s for the observer to hear the B note.

What is the frequency of the note being played on the piano as it approaches the observer?

• 500 Hz

• 343 Hz

• 494 Hz

• 440 Hz

What is the frequency that the observer hears when the train is moving towards them?

• 440 Hz

• 500 Hz

• 343 Hz

• 494 Hz

What is the speed of sound used in this problem?

• 500 m/s

• 400 m/s

• 343 m/s

• 300 m/s

Which variable represents the velocity of the observer in the Doppler effect equation?

• V source

• V observer

• V sound

• V train

What mathematical operation is performed to isolate V source in the equation?

• Multiplication

• Reciprocal

• Subtraction

• Addition

What sign is used in the denominator of the Doppler effect equation when the source is moving towards the observer?

• Divide

• Multiply

• Minus

• Plus

What is the final algebraic expression for V source in terms of V sound, F observed, and F original?

• V sound / (1 - F original / F observed)

• V sound * (1 - F original / F observed)

• V sound * (1 + F original / F observed)

• V sound / (1 + F original / F observed)

What is the calculated speed of the train car required to change the note from A to B?

• 40 m/s

• 37.5 m/s

• 30 m/s

• 50 m/s

What is the frequency of the note B that the observer hears?

• 500 Hz

• 440 Hz

• 494 Hz

• 343 Hz

What is the original frequency of the note A played by the piano?

• 343 Hz

• 500 Hz

• 494 Hz

• 440 Hz