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 39.6 kHz. A car is approaching him at a speed of 35.0 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 343 m/s. A) 5000 Hz
B) 4500 Hz
C) 8490 Hz
D) 9000 Hz
E) 4250 Hz
D
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Determine the magnitude of the Burger’s vector in MgO, shown in Figure 3.10, that has the NaCl crystal structure with a lattice parameter of 0.4212 nm, and compare the magnitude of this Burger’s vector to that of copper. Note that the Burger’s vector is in the [110] direction in MgO.
What will be an ideal response?
The centroid of the semicircular segment shown in the figure below (b 5 6 in.) is at coordinates (x, y)(in.):
(A) 4.5, 3.0
(B) 6.0, 4.0
(C) 5.5, 3.5
(D) 6.0, 3.23
In which season is Earth farthest from the Sun?
A. when it is autumn in North America B. when it is spring in North America C. when it is summer in North America D. when it is winter in North America
The speeds of 25 molecules are distributed as follows: 5 in the range from 2 to 3 m/s, 10 in the range from 3 to 4 m/s, 5 in the range from 4 to 5 m/s, 3 in the range from 5 to 6 m/s, 1 in the range from 6 to 7 m/s, and 1 in the range from 7 to 8 m/s. Their average speed is about:
A. 2 m/s B. 3 m/s C. 4 m/s D. 5 m/s E. 6 m/s