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
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