When a train leaves the station at a speed of 66m/s and whistles at a frequency of 1800Hz, set the sound velocity in the air is 330m/s and the sound frequency you will hear at the station will be ().
A. 2200 Hz
B. 1500Hz
C. 2400 Hz
D. 1000 Hz
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The sound wave is ().
A. Mechanical transverse wave
B. Mechanical longitudinal wave
C. Electromagnetic wave
D. X rays.
The intensity of wave is ().
A. energy of wave through unit area
B. energy of wave through unit area vertically
C. average energy per unit time through a section
D. average energy per unit time through per unit area vertically
The difference between two sound intensity level is 10dB, then the ratio of the two sound intensity is ().
A. 10
B. 20
C. 100
D. 2
The direction of additional pressure at the curved liquid surface is ().
A. pointing into the liquid
B. pointing out of the liquid
C. along the surface of the liquid
D. pointing to the center of curvature
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