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:

-ian

A suffix used to form adjectives and nouns indicating belonging or pertaining to a person, place, thing, or idea.

-cian

A suffix indicating a person's profession or a specialized field of expertise.

Nasolabial

Relating to the nose and the upper lip, particularly the crease or fold running from the side of the nose to the corner of the mouth.

Labionasal

Pertaining to both the lips and the nose; often used in speech pathology.