A Policeman in a Stationary Car Measures the Speed of Approaching

question 52

Multiple Choice

A policeman in a stationary car measures the speed of approaching cars by means of an ultrasonic device that emits a sound with a frequency of 41.2 kHz. A car is approaching him at a speed of 33.0 m/s. The wave is reflected by the car and interferes with the emitted sound producing beats. What is the frequency of the beats? The speed of sound in air is 330 m/s.

• A) 9.2 kHz
• B) 4.1 kHz
• C) 4.6 kHz
• D) 1.2 kHz
• E) 8.2 kHz

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Definitions:

Consciousness

The state of being aware of and able to think about one's own existence, sensations, thoughts, surroundings, and experiences.

Alertness

The state of being vigilant, awake, and attentive to the environment, enabling quick responses to changes or potential threats.

Content

Information or material contained within a medium, such as text, video, audio, or any other item that can be communicated.

Cognition

Encompasses all mental abilities and processes related to knowledge, understanding, reasoning, and awareness.