An alert physics student stands beside the tracks as a train...

Name: Problem 31, Chapter 14: College Physics
Uploaded: 2019-11-26T16:47:39-08:00
Duration: 2 min 36 s
Channel: Averell Hause
Description: An alert physics student stands beside the tracks as a train rolls slowly past. He notes that the frequency of the train whistle is 465 Hz when the train is approaching him and 441 Hz when the train is receding from him. Using these frequencies, he calculates the speed of the train. What value does he find?

An alert physics student stands beside the tracks as a train rolls slowly past. He notes that the frequency of the train whistle is 465 Hz when the train is approaching him and 441 Hz when the train is receding from him. Using these frequencies, he calculates the speed of the train. What value does he find?

An alert physics student stands beside the tracks as a train rolls slowly past. He notes that the frequency of the train whistle is 465 Hz when the train is approaching him and 441 Hz when
the train is receding from him. Using these frequencies, he calculates the speed of the train. What value does he find?

Key Concepts

Doppler Equations

Doppler Equations are the mathematical formulas that relate the observed frequency to the emitted frequency, the speed of the source, and the speed of sound. These equations are used to derive unknown variables, such as the velocity of the moving source, based on the measured frequency shifts. They are essential tools in analyzing and interpreting the effects of relative motion on wave phenomena.

Speed of Sound

The speed of sound is the rate at which sound waves propagate through a medium. This constant value, which depends on the medium's properties, plays a critical role in the Doppler Effect equations. Accurate calculations of frequency shifts always require a known speed of sound, as it directly influences the relationship between the source's speed and the observed frequency changes.

Doppler Effect

The Doppler Effect is a phenomenon observed when there is relative motion between a wave source and an observer, resulting in a perceived shift in the frequency of the waves. When the source approaches, the frequency appears higher, and when it recedes, the frequency appears lower. This effect is fundamental in wave mechanics and has applications across various fields, including astrophysics, radar, and medical imaging.

Relative Motion

Relative motion refers to the movement of the source and the observer in relation to each other. In the context of the Doppler Effect, the degree of the frequency shift depends on the velocity of the source relative to the observer. Understanding relative motion is crucial in calculating the actual speed of the moving object or determining the rate of change in the observed frequency.

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