Question

As a train approaches the next stop, the conductor blows the horn and applies the breaks on the train. What will a person standing at the train stop hear as the train approaches? (A) A decrease in the frequency and an increase in the intensity of the horn (B) An increase in the frequency and a decrease in the intensity of the horn (C) A decrease in both the frequency and intensity of the horn (D) An increase in both the frequency and intensity of the horn

Name: Problem 42, Chapter 14: Cracking The AP Physics 1 Exam
Uploaded: 2021-04-08T17:35:17-08:00
Duration: 1 min 18 s
Channel: Sachin Rao

   As a train approaches the next stop, the conductor blows the horn and applies the breaks on the train. What will a person standing at the train stop hear as the train approaches?
(A) A decrease in the frequency and an increase in the intensity of the horn
(B) An increase in the frequency and a decrease in the intensity of the horn
(C) A decrease in both the frequency and intensity of the horn
(D) An increase in both the frequency and intensity of the horn

Cracking The AP Physics 1 Exam

Robert Franek 1st Edition

Chapter 14, Problem 42

Instant Answer

Solved by Expert Sachin Rao

04/08/2021

Step 1

In this case, as the train approaches the person at the stop, the person perceives the sound of the horn with a frequency higher than the original frequency emitted from the train. This is due to the Doppler effect. Show more…

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As a train approaches the next stop, the conductor blows the horn and applies the breaks on the train. What will a person standing at the train stop hear as the train approaches? (A) A decrease in the frequency and an increase in the intensity of the horn (B) An increase in the frequency and a decrease in the intensity of the horn (C) A decrease in both the frequency and intensity of the horn (D) An increase in both the frequency and intensity of the horn

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Key Concepts

Doppler Effect

The Doppler effect refers to the change in frequency or wavelength of a wave in relation to an observer moving relative to the source of the wave. As the source approaches the observer, the sound waves compress, leading to a higher frequency (and thus a higher pitch). Conversely, as the source moves away, the sound waves expand, resulting in a lower frequency.

Sound Intensity and Distance Relationship

Sound intensity is the power carried by sound waves per unit area, which decreases with an increase in distance from the source due to the spreading of the wavefronts. As the source of sound comes closer to the observer, the intensity increases, making the sound seem louder.

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