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Author Question: A policeman in a stationary car measures the speed of approaching cars by means of an ultrasonic ... (Read 57 times)

future617RT

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  • Posts: 543
on: Jul 29, 2018
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

Question 2

A steel sphere with a radius of 2.0 m falls off a ship and sinks to a depth where the pressure is 15 MN/m2. The bulk modulus for steel is 1.61011 N/m2. What is the change in the radius of the sphere?
 
  A)
 
  0.021 mm
 
  B)
 
  4.2 mm
 
  C)
 
  0.42 mm
 
  D)
 
  0.19 mm
 
  E)
 
  0.063 mm


Bsand8

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Reply #1 on: Jul 29, 2018
Answer to Question 1

A

Answer to Question 2

E


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